Process for Separating Hydrogen from an Olefin Hydrocarbon Effluent Vapor Stream

ABSTRACT

One or more specific embodiments disclosed herein includes a method for separating hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream, employing a integrated heat exchanger, multiple gas-liquid separators, external refrigeration systems, and a rectifier attached to a liquid product drum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.17/966,314 filed on Oct. 14, 2022, which is a continuation-in-part ofU.S. application Ser. No. 17/377,895 filed on Jul. 16, 2021, which is acontinuation-in-part of U.S. application Ser. No. 17/191,427 filed onMar. 3, 2021, which is a continuation of U.S. application Ser. No.17/191,373 filed on Mar. 3, 2021, which is a continuation-in-part ofU.S. application Ser. No. 17/113,640 filed on Dec. 7, 2020, which is adivisional of U.S. application Ser. No. 15/988,601 filed on May 24,2018, which is a continuation-in-part of U.S. application Ser. No.15/600,758 filed on May 21, 2017, the disclosures of which are hereinincorporated by reference in their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND 1. Field of Inventions

The field of this application and any resulting patent is processes andsystems for separating hydrogen from an olefin hydrocarbon vapor stream.

2. Description of Related Art

Various processes and systems have been proposed and utilized forseparating hydrogen from an olefin hydrogen rich compressed effluentvapor stream, including some of the processes and systems disclosed inthe references appearing on the face of this patent. However, thoseprocesses and systems lack all the steps or features of the processesand systems covered by any patent claims below. As will be apparent to aperson of ordinary skill in the art, any processes and systems coveredby claims of the issued patent solve many of the problems that prior artprocesses and systems have failed to solve. Also, the processes andsystems covered by at least some of the claims of this patent havebenefits that could be surprising and unexpected to a person of ordinaryskill in the art based on the prior art existing at the time ofinvention.

SUMMARY

One or more specific embodiments disclosed herein includes a process forthe separation of hydrogen from an olefin hydrocarbon rich compressedeffluent vapor stream from a dehydrogenation unit, comprising cooling acompressed effluent vapor stream in a heat exchanger; separatinghydrogen from olefin and heavy paraffinic components in the cooledcompressed effluent vapor stream in a first separator to provide a firstvapor stream and a first liquid stream; cooling the first vapor streamin the heat exchanger; separating hydrogen from olefin and heavyparaffinic components in the cooled first vapor stream in a secondseparator to provide a second vapor stream and a second liquid stream;warming the second vapor stream in the heat exchanger; isentropicallyexpanding, in a high-pressure expander, the second vapor stream, whereinthe pressure and temperature of the second vapor stream are lowered;warming the second vapor stream in the heat exchanger; compressing, in ahigh-pressure compressor, the second vapor stream; cooling the secondvapor stream in a first discharge cooler; dividing the second vaporstream into a gas product and a split stream; withdrawing the gasproduct; compressing, in a low-pressure compressor, the split stream;cooling the split stream in a second discharge cooler and furthercooling the split stream in the heat exchanger; isentropicallyexpanding, in a low-pressure expander, the split stream, wherein thepressure and temperature of the split stream are lowered; cooling aliquid paraffinic stream in the heat exchanger; combining the cooledliquid paraffinic stream with the expanded split stream to provide acombined feed, vaporizing the combined feed in the heat exchanger;withdrawing the vaporized combined feed; lowering the pressure of thefirst liquid stream in a control valve; partially vaporizing the firstliquid stream in the heat exchanger; flashing the partially vaporizedfirst liquid stream in a liquid product drum to provide a hydrogen-richgas, which travels to a rectifier connected to the liquid product drum;combining the hydrogen-rich gas and the second liquid stream in therectifier, further purifying the hydrogen-rich gas; warming thehydrogen-rich gas from the rectifier in the heat exchanger to provide aflashed vapor stream; pumping a third liquid stream from the liquidproduct drum to the heat exchanger, wherein it is warmed; and providinga liquid product.

One or more specific embodiments disclosed herein includes a process forthe separation of hydrogen from an olefin hydrocarbon rich compressedeffluent vapor stream from a dehydrogenation unit, comprising separatinghydrogen from olefin and heavy paraffinic components in the compressedeffluent vapor stream to provide a first vapor stream and a first liquidstream; separating hydrogen from olefin and heavy paraffinic componentsin the first vapor stream to provide a second vapor stream and a secondliquid stream; expanding and compressing the second vapor stream;dividing the second vapor stream into a gas product and a split stream;compressing and expanding the split stream; lowering the pressure of thefirst liquid stream; partially vaporizing the first liquid stream;flashing the partially vaporized first liquid stream in a liquid productdrum to provide a hydrogen-rich gas; and combining the hydrogen-rich gasand the second liquid stream in a rectifier.

One or more specific embodiments disclosed herein includes a process forthe separation of hydrogen from an olefin hydrocarbon rich compressedeffluent vapor stream from a dehydrogenation unit, comprising separatinghydrogen from olefin and heavy paraffinic components in the compressedeffluent vapor stream to provide a first vapor stream and a first liquidstream; separating hydrogen from olefin and heavy paraffinic componentsin the first vapor stream to provide a second vapor stream and a secondliquid stream; isentropically expanding, in a high-pressure expander,the second vapor stream; compressing, in a high-pressure compressor, thesecond vapor stream; dividing the second vapor stream into a gas productand a split stream; compressing, in a low-pressure compressor, the splitstream; and isentropically expanding, in a low-pressure expander, thesplit stream.

One or more specific embodiments disclosed herein includes a process forthe separation of hydrogen from an olefin hydrocarbon rich compressedeffluent vapor stream from a dehydrogenation unit, comprising cooling acompressed effluent vapor stream in a heat exchanger; separatinghydrogen from olefin and heavy paraffinic components in the cooledcompressed effluent vapor stream in a first separator to provide a firstvapor stream and a first liquid stream; cooling the first vapor streamin the heat exchanger; separating hydrogen from olefin and heavyparaffinic components in the cooled first vapor stream in a secondseparator to provide a second vapor stream and a second liquid stream;warming the second vapor stream in the heat exchanger to provide a gasproduct.

One or more specific embodiments disclosed herein includes a process forthe separation of hydrogen from an olefin hydrocarbon rich compressedeffluent vapor stream from a dehydrogenation unit, comprising cooling acompressed effluent vapor stream in a heat exchanger; separatinghydrogen from olefin and heavy paraffinic components in the cooledcompressed effluent vapor stream in a first separator to provide a firstvapor stream and a first liquid stream; cooling the first vapor streamin the heat exchanger; separating hydrogen from olefin and heavyparaffinic components in the cooled first vapor stream in a secondseparator to provide a second vapor stream and a second liquid stream;warming the second vapor stream in the heat exchanger to provide a gasproduct; lowering the pressure of the first liquid stream in a controlvalve; flashing the first liquid stream in a liquid product drum toprovide a hydrogen-rich gas, which travels to a rectifier connected tothe liquid product drum; dividing the second liquid stream into a firstliquid split stream and a second liquid split stream; lowering thepressure of the first liquid split stream in a control valve; partiallyvaporizing the first liquid split stream in the heat exchanger; flashingthe partially vaporized first liquid split stream in the liquid productdrum to provide additional hydrogen-rich gas, which travels to therectifier connected to the liquid product drum; combining thehydrogen-rich gas and the second liquid split stream in the rectifier,further purifying the hydrogen-rich gas; warming the purifiedhydrogen-rich gas from the rectifier in the heat exchanger to provide aflashed vapor stream; pumping a third liquid stream from the liquidproduct drum to the heat exchanger, wherein it is warmed to provide aliquid product; dividing a liquid paraffinic stream into a plurality ofliquid paraffinic streams; lowering the pressure of each of theplurality of liquid paraffinic streams in respective control valves;introducing each of the plurality of liquid paraffinic streams intorespective thermosiphon vessels to provide a plurality of vaporparaffinic streams and a plurality of secondary liquid paraffinicstreams; circulating each of the plurality of secondary liquidparaffinic streams from the bottom of each thermosiphon vessel, throughthe heat exchanger, and back to each respective thermosiphon vessel as aplurality of two-phase paraffinic streams, wherein a vapor phase of eachof the plurality of two-phase paraffinic streams combines with each ofthe plurality of vapor paraffinic streams, and wherein a liquid phase ofeach of the plurality of two-phase paraffinic streams combines with eachof the plurality of secondary liquid paraffinic streams; heating each ofthe plurality of vapor paraffinic streams in the heat exchanger; andcombining each of the plurality of heated vapor paraffinic streams toprovide an alternative combined feed stream, wherein each of theplurality of heated vapor paraffinic streams are optionally compressedvia a compressor prior to being combined.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration, block flow diagram of a system forhydrogen separation shown as a part on and in an overall dehydrogenationsystem.

FIG. 2 is a schematic illustration, flow diagram of a system forhydrogen separation.

FIG. 2A is a schematic illustration, flow diagram of FIG. 2 , butshowing the optional use of a booster compressor.

FIG. 2B is a schematic illustration, flow diagram of FIG. 2 , butshowing the optional use of a non-driver I-Compander.

FIG. 2C is the schematic illustration, flow diagram of FIG. 2B, butshowing the optional use of a motor-driver I-Compander.

FIG. 2D is a schematic illustration, flow diagram showing a system forhydrogen separation using two separate expander/compressor sets inseries.

FIG. 3 is a schematic illustration, flow diagram of FIG. 2 , but showingthe optional use of an expander/electric generator system.

FIG. 4 is the schematic illustration, flow diagram of FIG. 2 with thealternative embodiment of the integrated main heat exchanger split intoa warm section and a cold section.

FIG. 5 is the schematic illustration, flow diagram of FIG. 2A with thealternative embodiment of the integrated main heat exchanger split intoa warm section and a cold section.

FIG. 6 is the schematic illustration, flow diagram of FIG. 2B with thealternative embodiment of the integrated main heat exchanger split intoa warm section and a cold section.

FIG. 7 is the schematic illustration, flow diagram of FIG. 2C with thealternative embodiment of the integrated main heat exchanger split intoa warm section and a cold section.

FIG. 8 is the schematic illustration, flow diagram of FIG. 2D with thealternative embodiment of the integrated main heat exchanger split intoa warm section and a cold section.

FIG. 9 is the schematic illustration, flow diagram of FIG. 3 with thealternative embodiment of the integrated main heat exchanger split intoa warm section and a cold section.

FIG. 10 is a schematic illustration, flow diagram of FIG. 9 , butshowing the optional use of an external refrigeration system using amixed refrigerant.

FIG. 11 is a schematic illustration, flow diagram of FIG. 9 , butshowing the optional use of an external cascade refrigeration systemhaving two or more refrigeration cycles.

FIG. 12 is a schematic illustration, flow diagram of FIG. 10 , butshowing an alternative “no recycle gas” embodiment that does not utilizea recycled gas stream.

FIG. 13 illustrates an additional embodiment of the separation system ofthe processing unit shown in FIG. 12 , further comprising a deethanizersystem and a propylene/propane splitter system.

FIG. 14 illustrates an alternative embodiment of a refrigeration processfor a rectifier column condenser.

FIG. 15 illustrates an alternative embodiment of a refrigeration processwherein refrigeration may be obtained from a cold section of anintegrated main heat exchanger.

DETAILED DESCRIPTION 1. Introduction

A detailed description will now be provided. The purpose of thisdetailed description, which includes the drawings, is to satisfy thestatutory requirements of 35 U.S.C. § 112. For example, the detaileddescription includes a description of the inventions defined by theclaims and sufficient information that would enable a person havingordinary skill in the art to make and use the inventions. In thefigures, like elements are generally indicated by like referencenumerals regardless of the view or figure in which the elements appear.The figures are intended to assist the description and to provide avisual representation of certain aspects of the subject matter describedherein. The figures are not all necessarily drawn to scale, nor do theyshow all the structural details of the systems, nor do they limit thescope of the claims.

Each of the appended claims defines a separate invention which, forinfringement purposes, is recognized as including equivalents of thevarious elements or limitations specified in the claims. Depending onthe context, all references below to the “invention” may in some casesrefer to certain specific embodiments only. In other cases, it will berecognized that references to the “invention” will refer to the subjectmatter recited in one or more, but not necessarily all, of the claims.Each of the inventions will now be described in greater detail below,including specific embodiments, versions, and examples, but theinventions are not limited to these specific embodiments, versions, orexamples, which are included to enable a person having ordinary skill inthe art to make and use the inventions when the information in thispatent is combined with available information and technology. Variousterms as used herein are defined below, and the definitions should beadopted when construing the claims that include those terms, except tothe extent a different meaning is given within the specification or inexpress representations to the Patent and Trademark Office (PTO). To theextent a term used in a claim is not defined below or in representationsto the PTO, it should be given the broadest definition persons havingskill in the art have given that term as reflected in any printedpublication, dictionary, or issued patent.

2. Selected Definitions

Certain claims include one or more of the following terms which, as usedherein, are expressly defined below.

The term “olefin hydrocarbon” as used herein is defined as anunsaturated hydrocarbon that contains at least one carbon-carbon doublebond. The term “compressed effluent vapor stream” as used herein isdefined as an olefin-hydrogen effluent gas stream from a feedcompressor. In certain embodiments disclosed herein, a combined feedenters a dehydrogenation unit to create an effluent gas stream thatcontains hydrogen, olefins, and heavy hydrocarbon components. Theeffluent gas stream in these embodiments is a low-pressure effluentstream. An example of a dehydrogenation unit is OLEFLEX™, which is abrand name for a dehydrogenation unit (OLEFLEX™ is a trademark of UOPInc. of Des Plaines, Ill.).

In certain embodiments disclosed herein, the compressed effluent vaporstream is referred to as a reactor effluent. Further, in certainembodiments, the reactor effluent enters a process for hydrogenseparation at 35° C.-52° C. and 0.5-1.2 MPa(g).

The term “compressor” as used herein is defined as a mechanical devicethat increases the pressure of a gas by reducing its volume. In certainembodiments disclosed herein, the feed compressor is also referred to asthe reactor effluent compressor unit.

The term “heat exchanger” as used herein is defined as a device thattransfers or “exchanges” heat from one matter to another. In certainembodiments disclosed herein, the heat exchanger is referred to as theintegrated main heat exchanger. Further, in certain embodimentsdisclosed herein, there may be more than one heat exchanger or only oneheat exchanger. Also, in certain embodiments, the heat exchanger may becomposed of brazed aluminum heat exchanger cores. In at least onespecific embodiment disclosed herein, the integrated main heat exchangerhas warm stream passes, and it has cold stream passes. Additionally, incertain embodiments with more than one heat exchanger, the heatexchangers may be configured in series or parallel.

The term “separator” as used herein is defined as a device used toseparate hydrogen from olefin and heavy paraffinic components. Incertain embodiments disclosed herein, gravity is used in a verticalvessel to cause liquid to settle to the bottom of the vessel, where theliquid is withdrawn. In the same embodiments, the gas part of themixture travels through a gas outlet at the top of the vessel. Further,in certain embodiments disclosed herein, there is more than oneseparator employed. In certain embodiments disclosed herein, eachseparator results in a majority of the olefin and paraffinic componentsbeing condensed to liquid and the hydrogen remaining vapor. A “paraffinhydrocarbon” is a saturated hydrocarbon having a general formulaC_(n)H_(2n+2). For example, in one embodiment disclosed herein, anoutlet stream enters a second separator and results in 99.8% vapor and0.2% liquid.

The term “first vapor stream” as used herein is mainly hydrogen gas. Inone specific embodiment disclosed herein, the first vapor stream isvapor stream from the first stage cold gas-liquid separator.

The term “first liquid stream” as used herein is composed of condensedolefin and paraffinic components. In certain embodiments disclosedherein, the first liquid stream is an olefin-rich liquid stream.Further, in certain embodiments disclosed herein, the first liquidstream is liquid stream from the first stage cold gas-liquid separator.

The term “second vapor stream” as used herein is composed of mainlyhydrogen gas. In certain embodiments disclosed herein, the second vaporstream has a temperature of −115° C. Further, in certain embodimentsdisclosed herein, the second vapor stream is a vapor stream from thesecond stage cold gas-liquid separator.

The term “second liquid stream” as used herein is composed of olefin andparaffinic components in liquid form. In one specific embodimentdisclosed herein, the second liquid stream is a liquid stream from thesecond stage cold gas-liquid separator.

The term “expander” as used herein is defined as a centrifugal or axialflow turbine through which a gas is isentropically expanded. In onespecific embodiment disclosed herein, cryogenic temperatures areachieved from refrigeration by expanding a high-pressure effluent gasstream using two-stage expanders. The term “cryogenic” as used herein isan adjective which means being or related to very low temperatures. Theterm “refrigeration” as used herein is defined as the process of movingheat from one location to another in controlled conditions.

An example of one type of expander configuration is anexpander/compressor configuration, which can be two independentexpander/compressor sets. In this example of an expander/compressorconfiguration, the two sets may be either two separate magnetic bearingtype expander/compressor sets or oil bearing type sets that share acommon lube oil system. For the expander configuration with two separateexpander/compressor sets, one set may be called a high-pressureexpander/compressor set that is configured as “post-compression.”Another set may be called a low-pressure expander/compressor set that isconfigured as “pre-compression.” “Post-compression” means that thecompressor is set to compress the gas stream after expansion.“Pre-compression” means that the compressor is set to compress the gasstream before expansion. In certain embodiments disclosed herein, thecomposition and mass flow of the stream to the high-pressure expanderand the high-pressure compressor remain substantially unchanged.Further, in the same embodiments, the composition and mass flow of thestream to the low-pressure expander and the low-pressure compressorremain substantially unchanged.

In other embodiments, a booster compressor may be added at the dischargeof a high-pressure compressor. The term “booster compressor” as usedherein refers to an additional compressor that provides additionalpressure. In one specific embodiment disclosed herein, a boostercompressor is added to achieve the required refrigeration for aneffluent gas stream. Further, in the same embodiment, the boostercompressor may be an independent compressor driven by either electricalmotor or another type of driver. The term “motor” as used herein isdefined as an electrical machine that converts electrical energy intomechanical energy.

In other embodiments, the high-pressure expander, the low-pressureexpander, the high-pressure compressor, and the low-pressure compressorare mounted to a common bull gear to form a non-driver I-Compander. Theterm “bull gear” as used herein is defined as any large driving gearamong smaller gears. In yet another embodiment, an electrical motor maybe added to the bull gear to provide additional power for thecompressor(s) to boost the pressure of a gas stream.

Another example of an expander configuration is an expander/electricgenerator configuration. The term “electric generator” as used herein isdefined as a device that converts mechanical energy into electricalenergy. In certain embodiments disclosed herein, there may be twoseparate expander/electric generator sets. Further, in thoseembodiments, the output power from the high-pressure expander drives itscorresponding electric generator to produce electricity. Likewise, inthose same embodiments, the output power from the low-pressure expanderdrives its corresponding electric generator to produce electricity.

The term “refrigerant compressor” as used herein refers to an additionalcompressor that provides additional pressure. In certain embodimentsdisclosed herein, an external refrigeration system comprising a singleor multi-stage refrigerant compressor may be added to the separationsystem to provide the necessary refrigeration. In one specificembodiment disclosed herein, a refrigerant compressor may be added tothe system to achieve the required refrigeration for an effluent gasstream. Further, in the same embodiment, the refrigerant compressor maybe an independent compressor driven by either electrical motor oranother type of driver. Further still, in the same embodiment, therefrigerant compressor system may include multiple stages of compressionwith a discharge cooler after each compressor stage and a dischargevapor/liquid separator after each discharge cooler.

The term “gas product” as used herein is defined as a hydrogen-rich gasproduct stream, which is sent to a downstream production facility. Inone specific embodiment disclosed herein, the gas product is net gasproduct. In one example, the gas product contains primarily the hydrogenas well as the methane and ethane lighter hydrocarbons from the reactoreffluent stream minus the material produced internally as recycle gas.In this example, the specifications for the gas product are as follows:

PDH Unit Hydrogen, mole percent minimum 92.5 Total C₃₊ olefins, mole %maximum 0.055 Temperature, C. 36 Pressure, MPa(g) 0.60

The term “split stream” as used herein refers to a hydrogen-rich stream.In one specific embodiment disclosed herein, the split stream is arecycle gas. In one example, the recycle gas meets the followingspecifications:

PDH Unit Hydrogen, mole percent minimum 92.5 Total Olefins, mole percent 0.1 maximum C3+ Olefins, mole percent 0.05 maximum

The term “liquid paraffinic stream” as used herein refers to a liquidhydrocarbon stream of primarily propane, isobutane, or a mixture ofprimarily both. Propane is a three-carbon alkane with the molecularformula C₃H₈. Isobutane is the simplest alkane with a tertiary carbon,and it has the molecular formula C₄H₁₀. In one specific embodimentdisclosed herein, the liquid paraffinic stream is the fresh feed. In oneexample, the liquid paraffinic stream has a temperature of 52° C. and apressure of 2.06 MPa(g).

The term “control valve” as used herein is defined as a valve used tocontrol fluid flow by varying the size of the flow passage. In onespecific embodiment disclosed herein, the control valve is used to lowerthe pressure of the fluid flow. The term “liquid product drum” as usedherein is defined as a device used to separate a vapor-liquid mixture.In certain embodiments disclosed herein, a liquid product drum isattached to a rectifier. In these certain embodiments, the liquidproduct drum is used for flashing a partially vaporized liquid stream.The term “flashing” as used herein refers to “flash evaporation,” whichis defined as the partial vapor that occurs when a saturated liquidstream undergoes a reduction in pressure by passing through a throttlingvalve or other throttling device. In one example, the temperature of theliquid product drum is maintained at around 0° C. so that the liquidproduct drum may be composed of carbon steel.

In one specific embodiment, once in the liquid product drum, lightcomponents such as hydrogen, methane, and ethane, flash out from theliquid and travel upward through a rectifier located on top of theliquid product drum. The term “rectifier” as used herein is defined as apacked column used for “rectification.” In “rectification,” vapor andliquid are passed countercurrent to one another through a specialapparatus, sometimes known as a rectifier, in which there are multiplepoints of contact between the two phases. The countercurrent movement isaccompanied by heat and mass exchanges. In one example, the rectifier isa hollow vertical cylinder, within which there are irregularly shapedmaterials, known collectively as packing. The packing is used to enlargethe vapor-liquid interface.

The term “final liquid product” as used herein refers to an olefin-richliquid product stream. In one specific embodiment disclosed herein, thefinal liquid product is liquid product stream 307. In one example, thefinal liquid product contains primarily the propylene and heavierhydrocarbons from a reactor effluent stream, meeting the followingspecifications:

Propane + propylene recovery, % 99.9 Temperature, C. 50 ± 5° C.Pressure, MPa(g) 4.0

The “flashed vapor stream” is the vapor from the liquid product drum. Incertain embodiments disclosed herein, the flashed vapor stream may berecycled back to the reactor effluent compressor unit for recovery ofany hydrocarbons in the flashed vapor stream.

The term “coldbox” as used herein is defined as a box designed tocontain low-temperature and cryogenic equipment and parts. In certainembodiments disclosed herein, the coldbox is filled with insulationmaterial and purged with nitrogen to provide cold insulation. In certainembodiments, the coldbox may contain the heat exchanger, the separators,the liquid product drum and rectifier, as well as the associated piping.In the same embodiments, control valves can either be enclosed within orinstalled outside of the coldbox.

3. Certain Specific Embodiments

Now, certain specific embodiments are described, which are by no meansan exclusive description of the inventions. Other specific embodiments,including those referenced in the drawings, are encompassed by thisapplication and any patent that issues therefrom.

One or more specific embodiments disclosed herein includes a process forthe separation of hydrogen from an olefin hydrocarbon rich compressedeffluent vapor stream from a dehydrogenation unit, comprising cooling acompressed effluent vapor stream in a heat exchanger; separatinghydrogen from olefin and heavy paraffinic components in the cooledcompressed effluent vapor stream in a first separator to provide a firstvapor stream and a first liquid stream; cooling the first vapor streamin the heat exchanger; separating hydrogen from olefin and heavyparaffinic components in the cooled first vapor stream in a secondseparator to provide a second vapor stream and a second liquid stream;warming the second vapor stream in the heat exchanger; isentropicallyexpanding, in a high-pressure expander, the second vapor stream, whereinthe pressure and temperature of the second vapor stream are lowered;warming the second vapor stream in the heat exchanger; compressing, in ahigh-pressure compressor, the second vapor stream; cooling the secondvapor stream in a first discharge cooler; dividing the second vaporstream into a gas product and a split stream; withdrawing the gasproduct; compressing, in a low-pressure compressor, the split stream;cooling the split stream in a second discharge cooler and furthercooling the split stream in the heat exchanger; isentropicallyexpanding, in a low-pressure expander, the split stream, wherein thepressure and temperature of the split stream are lowered; cooling aliquid paraffinic stream in the heat exchanger; combining the cooledliquid paraffinic stream with the expanded split stream to provide acombined feed; vaporizing the combined feed in the heat exchanger;withdrawing the vaporized combined feed; lowering the pressure of thefirst liquid stream in a control valve; partially vaporizing the firstliquid stream in the heat exchanger; flashing the partially vaporizedfirst liquid stream in a liquid product drum to provide a hydrogen-richgas, which travels to a rectifier connected to the liquid product drum;combining the hydrogen-rich gas and the second liquid stream in therectifier, further purifying the hydrogen-rich gas; warming thehydrogen-rich gas from the rectifier in the heat exchanger to provide aflashed vapor stream; pumping a third liquid stream from the liquidproduct drum to the heat exchanger, wherein it is warmed; and providinga liquid product.

One or more specific embodiments disclosed herein includes a process forthe separation of hydrogen from an olefin hydrocarbon rich compressedeffluent vapor stream from a dehydrogenation unit, comprising separatinghydrogen from olefin and heavy paraffinic components in the compressedeffluent vapor stream to provide a first vapor stream and a first liquidstream; separating hydrogen from olefin and heavy paraffinic componentsin the first vapor stream to provide a second vapor stream and a secondliquid stream; expanding and compressing the second vapor stream;dividing the second vapor stream into a gas product and a split stream;compressing and expanding the split stream; lowering the pressure of thefirst liquid stream; partially vaporizing the first liquid stream;flashing the partially vaporized first liquid stream in a liquid productdrum to provide a hydrogen-rich gas; and combining the hydrogen-rich gasand the second liquid stream in a rectifier.

One or more specific embodiments disclosed herein includes a process forthe separation of hydrogen from an olefin hydrocarbon rich compressedeffluent vapor stream from a dehydrogenation unit, comprising separatinghydrogen from olefin and heavy paraffinic components in the compressedeffluent vapor stream to provide a first vapor stream and a first liquidstream; separating hydrogen from olefin and heavy paraffinic componentsin the first vapor stream to provide a second vapor stream and a secondliquid stream; isentropically expanding, in a high-pressure expander,the second vapor stream; compressing, in a high-pressure compressor, thesecond vapor stream; dividing the second vapor stream into a gas productand a split stream; compressing, in a low-pressure compressor, the splitstream; and isentropically expanding, in a low-pressure expander, thesplit stream.

One or more specific embodiments disclosed herein includes a process forthe separation of hydrogen from an olefin hydrocarbon rich compressedeffluent vapor stream from a dehydrogenation unit, comprising coolingthe compressed effluent vapor stream in a heat exchanger; separatinghydrogen from olefin and heavy paraffinic components in the cooledcompressed effluent vapor stream to provide a first vapor stream and afirst liquid stream; cooling the first vapor stream in the heatexchanger; separating hydrogen from olefin and heavy paraffiniccomponents in the cooled first vapor stream to provide a second vaporstream and a second liquid stream; warming the second vapor stream inthe heat exchanger; expanding the second vapor stream; warming thesecond vapor stream in the heat exchanger; compressing the second vaporstream; dividing the second vapor stream into a gas product and a splitstream; compressing the split stream; cooling the split stream in theheat exchanger; expanding the split stream; cooling a liquid paraffinicstream in the heat exchanger; combining the cooled liquid paraffinicstream with the expanded split stream to provide a combined feed;vaporizing the combined feed in the heat exchanger; partially vaporizingthe first liquid stream in the heat exchanger; flashing the partiallyvaporized first liquid stream in a liquid product drum to provide ahydrogen-rich gas; warming the hydrogen-rich gas in the heat exchangerto provide a flashed vapor stream; and pumping a third liquid streamfrom the liquid product drum to the heat exchanger, wherein it iswarmed.

In any one of the processes or systems disclosed herein, the heatexchanger may be a single heat exchanger.

In any one of the processes or systems disclosed herein, the heatexchanger may be comprised of one or more brazed aluminum heat exchangercores.

In any one of the processes or systems disclosed herein, the compressedeffluent vapor stream may be comprised of hydrogen, paraffinichydrocarbons, and propylene or isobutylene.

In any one of the processes or systems disclosed herein, the compressedeffluent vapor stream may be comprised of hydrogen, paraffinichydrocarbons, and a mixture of propylene and isobutylene.

In any one of the processes or systems disclosed herein, the liquidparaffinic stream may be comprised of either propane, isobutane, or acombination of propane and isobutane.

In any one of the processes or systems disclosed herein, the process maybe performed without the employment of external refrigeration.

In any one of the processes or systems disclosed herein, a boostercompressor may be employed to provide additional pressure to the secondvapor stream from the high-pressure compressor.

In any one of the processes or systems disclosed herein, thehigh-pressure expander, the low-pressure expander, the high-pressurecompressor, and the low-pressure expander may be mounted to a bull gear.

In any one of the processes or systems disclosed herein, a motor may beemployed to drive the bull gear.

In any one of the processes or systems disclosed herein, one or moreelectric generators may be driven by the power produced in thehigh-pressure expander, low-pressure expander, or both expanders.

In any one of the processes or systems disclosed herein, thehigh-pressure expander and the low-pressure expander may be configuredin series.

In any one of the processes or systems disclosed herein, thehigh-pressure compressor and the low-pressure compressor may beconfigured into two or more stages in series.

In any one of the processes or systems disclosed herein, thehigh-pressure compressor may be driven by the power produced in thehigh-pressure expander.

In any one of the processes or systems disclosed herein, thelow-pressure compressor may be driven by the power produced in thelow-pressure expander.

In any one of the processes or systems disclosed herein, a coldbox maybe employed to contain all low-temperature and cryogenic equipment andparts.

In any one of the processes or systems disclosed herein, the withdrawncombined feed may be employed as a feed stream to a dehydrogenationreactor.

In any one of the processes or systems disclosed herein, the withdrawnliquid product may be introduced into a product storage system.

In any one of the processes or systems disclosed herein, the flashedvapor stream may be recycled to a feed compressor.

In any one of the processes or systems disclosed herein, the liquidproduct drum may be maintained at a temperature such that the liquidproduct drum may be composed of carbon steel.

In any one of the processes or systems disclosed herein, the compositionand mass flow of the second vapor stream to the high-pressure expanderand the high-pressure compressor may remain substantially unchanged.

In any one of the processes or systems disclosed herein, the compositionand mass flow of the split stream to the low-pressure expander and thelow-pressure compressor may remain substantially unchanged.

In any one of the processes or systems disclosed herein, thehigh-pressure expander and high-pressure compressor set and thelow-pressure expander and low-pressure compressor set may be magneticbearing type expander/compressor sets.

In any one of the processes or systems disclosed herein, thehigh-pressure expander and high-pressure compressor set and thelow-pressure expander and low-pressure compressor set may be oil bearingtype sets that share a common lube oil system.

One or more specific embodiments disclosed herein includes a separationsystem which utilizes a process for the separation of hydrogen from anolefin hydrocarbon rich compressed effluent vapor stream from adehydrogenation unit comprising a heat exchanger for cooling thecompressed effluent vapor stream, cooling the first vapor product,warming the second vapor product, reheating the second vapor product,cooling the split stream, cooling a liquid paraffinic feed for use inthe reactor, vaporizing the combined stream, partially vaporizing thefirst liquid product, warming the hydrogen-rich gas from the rectifier,and warming the flashed liquid stream from the liquid product drum; afirst separator in which the cooled compressed effluent vapor stream isseparated to provide a first vapor product and a first liquid product; asecond separator in which the cooled first vapor product is separated toprovide a second vapor product and a second liquid product; ahigh-pressure expander for isentropically expanding the second vaporproduct; a high-pressure compressor for compressing the second vaporproduct; a low-pressure compressor for compressing the split stream; alow-pressure expander for isentropically expanding the split stream; arectifier for flashing the partially vaporized first liquid product toprovide a hydrogen-rich gas and combining the hydrogen-rich gas with thesecond liquid product.

4. Specific Embodiments in the Figures

The drawings presented herein are for illustrative purposes only and arenot intended to limit the scope of the claims. Rather, the drawings areintended to help enable one having ordinary skill in the art to make anduse the claimed inventions.

Referring to FIGS. 1-3 , a specific embodiment, e.g., version orexample, of a system for hydrogen separation from an olefin hydrocarbonrich compressed effluent vapor stream is illustrated. These figures mayshow features which may be found in various specific embodiments,including the embodiments shown in this specification and those notshown.

FIG. 1 shows a system for hydrogen separation, processing unit 100, witha dehydrogenation unit 102 and a reactor effluent compressor unit 104. Afresh feed 200 is a liquid paraffinic stream mainly composed of propane,isobutane, or a mixture of propane and isobutane. Fresh feed 200 ismixed with a recycle gas 220 (not shown), which is produced within theprocessing unit 100. Recycle gas 220 contains primarily hydrogen. Thecombination of fresh feed 200 and recycle gas 220 is vaporized withinthe processing unit 100 and emerges as a combined feed 202. The combinedfeed 202 enters the dehydrogenation unit 102, where the combined feed202 is dehydrogenated resulting in an effluent gas stream 204. Effluentgas stream 204 is a low-pressure effluent stream composed of hydrogen,olefins, and other hydrocarbons. Effluent gas stream 204 is then mixedwith a flash drum vapor 206, which is primarily hydrogen, to form a feedgas stream 208. The feed gas stream 208 enters the reactor effluentcompressor unit 104, where the feed gas stream 208 has its pressureincreased and then its temperature lowered before entering processingunit 100. A reactor effluent 210 exits the reactor effluent compressorunit 104 containing a mixture of hydrogen and hydrocarbons. There aretwo product streams produced from the processing unit 100. One is ahydrogen-rich gas product stream, referred to as a net gas product 212,and the other is an olefin-rich liquid product stream, referred to as aliquid product 214, which has a boosted pressure.

The processing unit 100 is a system design and flow system that can beconnected to a propane dehydrogenation (PDH) unit, an isobutanedehydrogenation (BDH) unit, or a propane/isobutane dehydrogenation(PBDH) unit for hydrogen separation from the reactor effluent. Theprocess conditions (temperature, pressure, composition) are differentfor PDH, BDH, and PBDH, but the basic process flow scheme may be thesame. Illustrative process conditions at key points are listed in thetables below.

TABLE 1 An Example of Process Conditions of the Key Streams for a PDHPlant Stream No. 200 202 204 206 210 214 212 Stream Name Effluent FlashNet Fresh Combined Gas Drum Reactor Liquid Gas Feed Feed Stream VaporEffluent Product Product Pressure kPa · G 2200 350 5 5 1190 4000 590Temperature ° C. 52 37 43 37 43 49 43 Hydrogen Mole % 0.0000 H2/HCBN45.6105 70.9685 45.6936 0.0545 95.6074 Methane Mole % 0.0000 Ratio:2.6676 24.9248 2.7406 1.3315 4.1340 Ethylene Mole % 0.0000 0.42-0.50.1062 0.1596 0.1064 0.1820 0.0230 Ethane Mole % 0.7089 2.0304 1.35302.0282 3.7273 0.1681 Propylene Mole % 0.7793 15.9163 1.0486 15.867630.3881 0.0339 Propane Mole % 98.3613 33.5518 1.5445 33.4469 64.09280.0336 Propadiene Mole % 0.0000 0.0024 0.0001 0.0024 0.0047 0.0000Methyl acetylene Mole % 0.0000 0.0103 0.0004 0.0102 0.0196 0.0000Isobutane Mole % 0.1407 0.0472 0.0003 0.0470 0.0902 0.0000 IsobutyleneMole % 0.0065 0.0263 0.0001 0.0262 0.0503 0.0000 1-butene Mole % 0.00000.0006 0.0000 0.0006 0.0011 0.0000 Normal butane Mole % 0.0034 0.00020.0000 0.0002 0.0004 0.0000 Cis-2-butene Mole % 0.0000 0.0006 0.00000.0006 0.0011 0.0000 Trans-2-butene Mole % 0.0000 0.0007 0.0000 0.00070.0013 0.0000 Benzene Mole % 0.0000 0.0254 0.0000 0.0253 0.0485 0.0000Toluene Mole % 0.0000 0.0034 0.0000 0.0034 0.0065 0.0000 Xylene Mole %0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 (as p-xylene) Heavy Mole %0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 hydrocarbons (as anthracene)Notes: 1. Liquid product 214 to have >99.9% C3 Recovery 2. Net gasproduct 212 to have Minimum H2 > 92.5%; Max Total Olefins < 0.1%; C3 +Olefins, <0.05%

TABLE 2 An Example of Process Conditions of the Key Streams for a BDHPlant Stream No. 200 202 204 206 210 214 212 Stream Name Effluent FlashNet Fresh Combined Gas Drum Reactor Liquid Gas Feed Feed Stream VaporEffluent Product Product Pressure kPa · G 783 350 7 7 599 906 481Temperature ° C. 49 37 43 35 39 47 39 Hydrogen Mole % 0.0000 H2/HCBN47.8013 72.8813 47.8426 0.0525 93.9978 Methane Mole % 0.0000 Ratio:2.8804 19.7952 2.9081 0.4244 5.2564 Ethylene Mole % 0.0000 0.3-0.40.0041 0.0185 0.0041 0.0038 0.0043 Ethane Mole % 0.0000 0.1536 0.48720.1541 0.1980 0.1106 Propylene Mole % 0.0000 0.4072 0.2578 0.4069 0.77900.0474 Propane Mole % 0.7046 1.4840 0.8252 1.4829 2.8683 0.1446Propadiene Mole % 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Methylacetylene Mole % 0.0000 0.0001 0.0000 0.0001 0.0002 0.0000 IsobutaneMole % 97.5005 26.1652 3.5254 26.1280 52.9086 0.2912 Isobutylene Mole %0.0018 20.0619 2.1378 20.0324 40.6490 0.1441 1-butene Mole % 0.00000.1178 0.0116 0.1177 0.2389 0.0007 Normal butane Mole % 1.7931 0.58000.0408 0.5792 1.1776 0.0019 Cis-2-butene Mole % 0.0000 0.1308 0.00750.1306 0.2657 0.0003 Trans-2-butene Mole % 0.0000 0.1875 0.0117 0.18720.3808 0.0005 Benzene Mole % 0.0000 0.0044 0.0000 0.0044 0.0089 0.0000Toluene Mole % 0.0000 0.0044 0.0000 0.0044 0.0089 0.0000 Xylene Mole %0.0000 0.0174 0.0000 0.0174 0.0355 0.0000 (as p-xylene) Heavy Mole %0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 hydrocarbons (as anthracene)Notes: 1. Liquid product 214 to have >90% C4 Recovery 2. Net gas product212 to have Minimum H2 > 90%; Max C4 + Olefins < 0.03%

TABLE 3 An Example of Process Conditions of the Key Streams for a PBDHPlant Stream No. 200 202 204 206 210 214 212 Stream Name Effluent FlashNet Fresh Combined Gas Drum Reactor Liquid Gas Feed Feed Stream VaporEffluent Product Product Pressure kPa · G 1830 260 5 5 1070 4240 505Temperature ° C. 37 48 43 48 51 35 43 Hydrogen Mole % 0.0000 H2/HCBN45.9920 79.7057 46.0635 0.0497 96.6271 Methane Mole % 0.0000 Ratio:2.1818 18.8848 2.2172 1.1821 3.2835 Ethylene Mole % 0.0000 0.3-0.40.0159 0.0192 0.0159 0.0274 0.0031 Ethane Mole % 0.0013 0.6943 0.35760.6936 1.2766 0.0526 Propylene Mole % 0.4579 6.1041 0.2484 6.091711.6320 0.0115 Propane Mole % 56.0496 23.3764 0.7083 23.3283 44.56640.0219 Propadiene Mole % 0.0000 0.0004 0.0000 0.0004 0.0008 0.0000Methyl acetylene Mole % 0.0000 0.0017 0.0000 0.0017 0.0033 0.0000Isobutane Mole % 42.6054 11.4073 0.0468 11.3832 21.7572 0.0001Isobutylene Mole % 0.0207 9.5945 0.0280 9.5742 18.2998 0.0001 1-buteneMole % 0.0000 0.0739 0.0002 0.0737 0.1409 0.0000 Normal butane Mole %0.8652 0.3381 0.0006 0.3374 0.6449 0.0000 Cis-2-butene Mole % 0.00000.0806 0.0001 0.0804 0.1537 0.0000 Trans-2-butene Mole % 0.0000 0.11650.0002 0.1163 0.2223 0.0000 Benzene Mole % 0.0000 0.0089 0.0000 0.00890.0169 0.0000 Toluene Mole % 0.0000 0.0022 0.0000 0.0022 0.0041 0.0000Xylene Mole % 0.0000 0.0095 0.0000 0.0095 0.0182 0.0000 (as p-xylene)Heavy Mole % 0.0000 0.0019 0.0000 0.0019 0.0037 0.0000 hydrocarbons (asanthracene) Notes: 1. Liquid product 214 to have >95% C3 Recovery 2. Netgas product 212 to have Minimum H2 > 95%; Max Total Olefins < 0.1%; MaxC3 + Olefins < 0.05%

FIG. 2 shows the detailed configuration of the processing unit 100 withan integrated main heat exchanger 106, two separate expander/compressorsets (108/110 and 112/114), a first stage cold gas-liquid separator 116,a second stage cold gas-liquid separator 118, a liquid product drum 120,and a liquid product pump 122. Based on different process conditions,the integrated main heat exchanger 106 may, in the alternative, beconfigured into two or more heat exchangers in series or parallel.

The two separate expander/compressor sets (108/110 and 112/114) may betwo independent magnetic-bearing type or two sets of oil-bearing typethat share a common lube oil system. Each expander/compressor set(108/110 and 112/114) may be configured into two or more stages inseries setup depending on the pressure ratios of the expansion andcompression, the flow rates, and other factors.

Fresh feed 200 enters warm pass A1 at the upper warm end of theintegrated main heat exchanger 106 where the fresh feed 200 is cooled toa low temperature and exits pass A1 at the lower cold end of theintegrated main heat exchanger 106 as an outlet stream 216. The pressureof the outlet stream 216 is then reduced by a flow control valve 124 toa pressure that meets the required pressure of combined feed 202, whichfeeds the dehydrogenation unit 102 (not shown).

Outlet stream 218 of flow control valve 124 then returns to theintegrated main heat exchanger 106 via pass B1 where it mixes withrecycle gas 220 from the discharge of the low-pressure expander 112. Themixed stream of recycle gas 220 and outlet stream 218 travels upwardalong the channel of pass B1, where heat exchanging occurs between thecold stream pass B1 and warm stream passes A1, A2, A3, and A4. Beforeexiting through pass B1, the mixed stream is completely vaporized andbecomes a superheated vapor stream. The superheated vapor stream isreferred to as combined feed 202 after exiting pass B1. The pressure ofcombined feed 202 is maintained at a constant value by the feed of thedehydrogenation unit 102 (not shown). The combined feed 202 is thereactor feedstock for dehydrogenation unit 102 (not shown).

The reactor effluent 210, an olefin-hydrogen effluent stream from thereactor effluent compressor unit 104 (not shown), enters pass A2 at theupper warm end of the integrated main heat exchanger 106, where thestream is cooled to a low temperature as it flows through and exits passA2 in the middle of the integrated main heat exchanger 106. The coolingof the reactor effluent 210 as it travels through pass A2 is caused bycold stream passes B1 through B6. Outlet stream 222 from pass A2 entersthe first stage cold gas-liquid separator 116 with a low temperature, atwhich time a majority, >95%, of the olefin and heavy paraffiniccomponents in outlet stream 222 are condensed to liquid, which isseparated out as liquid stream 224. Further, almost all, >99% of thehydrogen from outlet stream 222 remains vapor, and the first stage coldgas-liquid separator 116 separates out the vapor as vapor stream 226.

The vapor stream 226 then flows back to the integrated main heatexchanger 106 through pass A3, where it is cooled to a lower temperatureby the time it exits pass A3 at the lower end of the integrated mainheat exchanger 106. The outlet stream 228 from pass A3 enters the secondstage cold gas-liquid separator 118, where almost all, >85%, of theolefin and heavy paraffinic components in outlet stream 228 arecondensed to liquid stream 230 and almost all, >99.95% of the hydrogenstays in vapor stream 232. The vapor stream 232 exits second stage coldgas-liquid separator 118 and returns to the integrated main heatexchanger 106 through pass B4, where vapor stream 232 is warmed beforeexiting pass B4 of the integrated main heat exchanger 106 as outletstream 234. Outlet stream 234 is superheated and enters thehigh-pressure expander 108, where it is expanded by “isentropic” gasexpansion process to a lower pressure and lower temperature to become acold stream 236. The output power from the high-pressure expander 108drives high-pressure compressor 110. The high-pressure expander 108 isequipped with an IGV (inlet guide vane) and bypass control valve 126 tomaintain a constant pressure at the inlet of high-pressure expander 108.

Cold stream 236 may or may not contain liquid. Cold stream 236 flowsdirectly into pass B3 at the lower cold end of the integrated main heatexchanger 106 and travels up pass B3, where it exchanges heat with warmstream passes A1, A2, A3, and A4. As cold stream 236 travels throughpass B3, it is warmed to a temperature close to the inlet temperaturesof passes A1, A2, A3, and A4 by the time it exits pass B3 at the upperwarm end of the integrated main heat exchanger 106. An outlet stream 238from pass B3 then flows to high-pressure compressor 110, where thepressure of outlet stream 238 is increased to meet the pressurerequirement of the net gas product 212. A discharge stream 240 fromhigh-pressure compressor 110, which contains primarily hydrogen andother lighter hydrocarbons (e.g. methane and ethane) from the reactoreffluent 210, is cooled down by a high-pressure compressor dischargecooler 128 before being split into two streams. One stream is the netgas product 212, which is sent to a downstream production facility. Thepressure of the net gas product 212 determines the discharge pressure ofthe high-pressure compressor 110. A pressure control valve 130 maintainsa minimum required discharge pressure of the high-pressure compressor110 to protect the high-pressure compressor 110 in case the pressure ofthe net gas product 212 is lost.

The second stream from the discharge of the high-pressure compressordischarge cooler 128 is a split stream 242. Split stream 242 is routedto the low-pressure compressor 114 where its pressure is boosted. Splitstream 242 is then cooled by a low-pressure compressor discharge cooler132, before entering warm stream pass A4 at the upper warm end of theintegrated main heat exchanger 106. Split stream 242 is cooled to a lowtemperature as it flows down and exits pass A4 at the middle of theintegrated main heat exchanger 106. An outlet stream 244 of pass A4 thenflows back to the low-pressure expander 112, where it is expanded to alower pressure and lower temperature through “isentropic” gas expansionprocess. The output power from the low-pressure expander 112 driveslow-pressure compressor 114. The low-pressure expander 112 dischargestream is recycle gas 220 that mixes with outlet stream 218 to becomecombined feed 202.

The low-pressure expander 112 is equipped with an IGV (inlet guide vane)and bypass control valve 134 to maintain a constant flow for recycle gas220 to mix with outlet stream 218 in order to meet the H₂/hydrocarbonmole ratio specified for combined feed 202. The H₂/hydrocarbon moleratio is defined as (moles of hydrogen in combined feed 202)/(moles ofhydrocarbon in combined feed 202). This ratio is typically specified bythe license of dehydrogenation reactors, for example the UOP's OLEFLEX™dehydrogenation reactor.

The pressure of combined feed 202 determines the discharge pressure ofthe low-pressure expander 112. A pressure control valve 136 maintains aminimum required pressure of the low-pressure expander 112 to protectthe low-pressure expander 112 from “flying out” in case the pressure ofthe combined feed 202 is lost.

Returning to the first stage cold gas-liquid separator 116, the pressureof the olefin-rich liquid stream 224 is reduced by level control valve138 before it enters pass B2 of the integrated main heat exchanger 106as cold stream 246. Cold stream 246 enters pass B2 at the lower cold endof the integrated main heat exchanger 106 where cold stream 246exchanges heat with the warm passes A1, A2, and A4 and becomes partiallyvaporized. This partially vaporized stream 248 exits pass B2 in themiddle of the integrated main heat exchanger 106 and flows to the liquidproduct drum 120. Once in the liquid product drum 120, light components,mainly hydrogen, methane, ethane, and maybe some C3+ components, flashout from the liquid and travel upward through the rectifier 140 locatedon the top of the liquid product drum 120. The upward travellinghydrogen-rich gas in the rectifier 140, which is a packed column, makescontact with the downward travelling colder liquid stream 230 from thesecond stage cold gas-liquid separator 118. Heat and mass transferringoccurs in the rectifier 140, and therefore the hydrogen-rich gas in therectifier 140 is further purified to meet the minimum hydrogen contentspecification of the flash drum vapor 206, before exiting the top of therectifier 140 as a vapor stream 250.

The pressure of the liquid product drum 120 is maintained by a pressurecontrol valve 142 on vapor stream 250 to a constant pressure to maximizethe recovery of olefin and heavy hydrocarbon components in the liquidproduct 214 and to meet the specification of the maximum allowablehydrogen content in the liquid product 214.

After the pressure control valve 142, a cold stream 252 contains certainolefin components in addition to the main light components hydrogen,methane, and ethane. The cold stream 252 enters cold stream pass B6 atthe lower cold end of the integrated main heat exchanger 106. As coldstream 252 travels up pass B6, it exchanges heat with the warm streampasses A1, A2, A3, and A4, and cold stream 252 is warmed to atemperature close to the inlet temperature of reactor effluent 210 orfresh feed 200 as it exits pass B6. The flash drum vapor 206 from passB6 then flows back to the inlet of the reactor effluent compressor unit104 (not shown).

The separated cold liquid stream 254 from the liquid product drum 120 ispumped by the liquid product pump 122 to a pressure that meets therequired pressure of the liquid product 214. The liquid level of theliquid product drum 120 is maintained by a level control valve 144.

The cold liquid product stream 256 then enters pass B5 at the middle ofthe integrated main heat exchanger 106. As the liquid product stream 256travels upward in pass B5, it exchanges heat with the warm passes A1,A2, and A4 and is warmed to a temperature defined by the liquid product214 specification as it exits pass B5 at the upper warm end of theintegrated main heat exchanger 106. The liquid product 214 is then sentto a production facility.

The liquid product drum 120 may be maintained at a temperature greaterthan −15° C., and therefore, liquid product drum 120 and liquid productpump 122 may be constructed of carbon steel for additional cost savings.

Liquid product drum 120 is elevated to a height to get enough NPSHa (netpositive suction head available) for the liquid product pump 122 toavoid cavitation damage to the liquid product pump 122.

Further, a coldbox 146 is designed to contain all low-temperatureequipment including the integrated main heat exchanger 106, the firststage cold gas-liquid separator 116, the second stage cold gas-liquidseparator 118, and the liquid product drum 120, as well as theassociated piping. Control valves 138, 119, 142, and 124 can either beenclosed within or installed outside of the coldbox 146. The coldbox 146is typically filled with insulation material and purged with nitrogen toprovide cold insulation for the low-temperature equipment and parts.

FIG. 2A shows the option of two separate expander/compressor sets(108/110 and 112/114) with an additional booster compressor 148 locatedat the discharge of the high-pressure compressor 110. The onlydifference between FIG. 2 and FIG. 2A is the addition of the boostercompressor 148, which is used to provide additional pressure todischarge stream 258 from high-pressure compressor 110. Further, boostercompressor 148 achieves the required refrigeration for the effluent gasstream 204, especially when the pressure difference between the reactoreffluent 210 and the net gas product 212 is not high enough to achievethe required refrigeration. The booster compressor 148 is an independentcompressor driven by either electrical motor or other type of driver.

FIG. 2B shows the non-driver I-Compander option. The only differencebetween FIG. 2 and FIG. 2B is that the high-pressure expander 108, thelow-pressure expander 112, the high-pressure compressor 110, and thelow-pressure compressor 114 are mounted to a common bull gear 150 toform a so called non-driver I-Compander 152. Depending on the pressureratios of expansion, flow rate, and other factors, each expander mayalso be set up in series with multiple stages available. Each compressorcan be configured into two or more stages in serial setup depending onthe pressure ratios of the compression, the flow rate, and otherfactors.

FIG. 2C shows the motor-driver I-Compander option. The only differencebetween FIG. 2B and FIG. 2C is the addition of a motor driver, electricmotor 154, to the bull gear 150 of the I-Compander 152. The power thatdrives the compressor(s) is from the high-pressure expander 108 and thelow-pressure expander 112, with additional power input from the electricmotor 154. The only difference between the “motor-driver option” and the“non-driver option” is the addition of the electric motor 154 thatprovides additional power for the compressor(s) to boost the pressure ofdischarge stream 240 and the pressure of outlet stream 244 high enoughto provide the required refrigeration. The power input to theI-Compander 152 by the electric motor 154 is needed especially when thepressure difference between the reactor effluent 210 and the net gasproduct 212 is not high enough to achieve the required refrigeration.

FIG. 2D shows the option of two separate expander/compressor sets (108a/110 a and 112 a/114 a) in series. In this embodiment, the two separateexpander/compressor sets (108 a/110 a and 112 a/114 a) replace thehigh-pressure expander/compressor set (108/110), as shown in FIG. 2 ,and the low-pressure expander/compressor set (112/114) is eliminated. Inthis embodiment, outlet stream 234 is superheated and enters expander108 a, where it is expanded by “isentropic” gas expansion process to alower pressure and lower temperature. Outlet stream 235 then entersexpander 112 a, where it is further expanded by “isentropic” gasexpansion process to a lower pressure and lower temperature. The outputpower from expander 108 a drives compressor 110 a. Expander 108 a isequipped with an IGV (inlet guide valve) and bypass control valve 126 tomaintain a constant pressure at the inlet of expander 108 a.Additionally, the output power from expander 112 a drives compressor 114a.

As further illustrated in FIG. 2D, outlet stream 237 then splits intotwo separate streams. The first split stream from outlet stream 237 iscold stream 236. Cold stream 236 may or may not contain liquid. Coldstream 236 flows directly into pass B3 at the lower cold end of theintegrated main heat exchanger 106 and travels up pass B3, where itexchanges heat with warm stream passes A1, A2, A3, and A4. As coldstream 236 travels through pass B3, it is warmed to a temperature closeto the inlet temperatures of passes A1, A2, A3, and A4 by the time itexits pass B3 at the upper warm end of the integrated main heatexchanger 106. In this embodiment, an outlet stream 238 from pass B3then flows to compressor 114 a, where the pressure of outlet stream 238is increased. Outlet stream 239 then enters compressor 110 a, where thepressure of outlet stream 239 is increased to meet the pressurerequirement of the net gas product 212. A discharge stream 240 fromcompressor 110 a, which contains primarily hydrogen and other lighterhydrocarbons (e.g. methane and ethane) from the reactor effluent 210, iscooled down by a high-pressure discharge cooler 128, which then becomesnet gas product 212, which is sent to a downstream production facility.The pressure of the net gas product 212 determines the dischargepressure of the compressor 110 a. A pressure control valve 130 maintainsa minimum required discharge pressure of the compressor 110 a to protectthe compressor 110 a in case the pressure of the net gas product 212 islost.

The second split stream from outlet stream 237 is recycle gas 220 thatmixes with outlet stream 218 to become combined feed 202. The pressureof combined feed 202 determines the discharge pressure of expander 112a. A pressure control valve 136 maintains a minimum required pressure ofthe expander 112 a to protect the expander 112 a from “flying out” incase the pressure of the combined feed 202 is lost.

FIG. 3 shows the expander/electric-generator option of the processingunit 100 in FIG. 1 . It illustrates configuration of the integrated mainheat exchanger 106, two separate expander/electric-generator sets(108/156 and 112/158), the first stage cold gas-liquid separator 116,the second stage cold gas-liquid separator 118, the liquid product drum120 and the liquid product pump 122. The differences between FIG. 3 andFIG. 2 include the configurations of the expander sets as well as thedetails identified below.

Stream 234 exits pass B4 of the integrated main heat exchanger 106superheated and enters the high-pressure expander 108, where stream 234is expanded to a lower pressure and lower temperature through aso-called “isentropic” gas expansion process. The output power from thehigh-pressure expander 108 drives electric generator 156 to produceelectricity. The high-pressure expander 108 is equipped with an IGV(inlet guide vanes) and bypass control valve 126 to maintain a constantpressure at the expander inlet.

The cold outlet stream 236 from the high-pressure expander 108 may ormay not contain liquid. It flows directly into pass B3 located at thelower cold end of the integrated main heat exchanger 106 and travels upin pass B3, where cold outlet stream 236 exchanges heat with the warmstream passes A1, A2, and A3. A side stream 260 is taken out from themiddle of pass B3 as feed to the low-pressure expander 112.

The outlet stream 262 of pass B3 flows through pressure control valve130 as net gas product 212 to a downstream production facility. Thepressure of the net gas product 212 determines the discharge pressure ofthe high-pressure expander 108. The pressure control valve 130 is tomaintain a minimum required discharge pressure of the high-pressureexpander 108 to protect the expander from “flying out” in case thepressure of the net gas product stream is lost.

The side-stream 260 from pass B3 is routed to the low-pressure expander112, where it is expanded to a lower pressure and lower temperaturethrough “isentropic” gas expansion process. The output power from thelow-pressure expander 112 drives electric generator 158 to produceelectricity.

The low-pressure expander 112 is equipped with an IGV (inlet guidevanes) and bypass control valve 134 to maintain a constant flow forstream 264, which is the required hydrogen-rich recycle gas flow to mixwith the liquid paraffinic stream 218 to meet the H2/HCBN mole ratiospecification for the combined feed 202. The H2/HCBN mole ratio isdefined as (moles of hydrogen in the combined feed 202)/(moles ofhydrocarbon in combined feed 202). This ratio is typically specified bythe license of dehydrogenation reactors, for example the UOP's OLEFLEX™dehydrogenation reactor.

The pressure of the combined feed 202 determines the discharge pressureof the low-pressure expander 112. A pressure control valve 136 isinstalled to maintain a minimum required pressure of the low-pressureexpander 112 to protect the expander from “flying out” in case thepressure of the combined feed 202 is lost. The stream 220 from pressurecontrol valve 136 commingles with stream 218 as detailed in thedescription of FIG. 2 . The stream 220 is the recycle gas stream thatmixes with stream 218 to become the combined feed 202.

Alternatively, certain embodiments may allow for the integrated mainheat exchanger 106 to be split into a warm section 106 a and a coldsection 106 b as shown in FIG. 4 . FIG. 4 is the schematic illustration,flow diagram of FIG. 2 with the alternative embodiment of the integratedmain heat exchanger 106 split into the warm section 106 a and the coldsection 106 b. The warm section 106 a and the cold section 106 b can becomposited of one or more brazed aluminum heat exchanger (BAHX) cores.As shown in FIG. 4 , a side stream 400 is taken from warm pass A1 at apoint at the upper end of the warm section 106 a. The flow of sidestream 400 is regulated by a control valve 300. The outlet stream 402from control valve 300 then flows into pass B1 at the lower end of thewarm section 106 a. Further, as shown in FIG. 4 , another side stream404 is taken from warm pass A1 at a point at the lower end of the warmsection 106 a. The flow of side stream 404 is regulated by a controlvalve 302. The outlet stream 406 from control valve 302 then flows intopass B1 lower in the warm section 106 a.

FIG. 5 is the schematic illustration, flow diagram of FIG. 2A with thealternative embodiment of the integrated main heat exchanger 106 splitinto the warm section 106 a and the cold section 106 b. The warm section106 a and the cold section 106 b can be composited of one or more brazedaluminum heat exchanger (BAHX) cores. As shown in FIG. 5 , a side stream400 is taken from warm pass A1 at a point at the upper end of the warmsection 106 a. The flow of side stream 400 is regulated by a controlvalve 300. The outlet stream 402 from control valve 300 then flows intopass B1 at the lower end of the warm section 106 a. Further, as shown inFIG. 5 , another side stream 404 is taken from warm pass A1 at a pointat the lower end of the warm section 106 a. The flow of side stream 404is regulated by a control valve 302. The outlet stream 406 from controlvalve 302 then flows into pass B1 lower in the warm section 106 a.

FIG. 6 is the schematic illustration, flow diagram of FIG. 2B with thealternative embodiment of the integrated main heat exchanger 106 splitinto the warm section 106 a and the cold section 106 b. The warm section106 a and the cold section 106 b can be composited of one or more brazedaluminum heat exchanger (BAHX) cores. As shown in FIG. 6 , a side stream400 is taken from warm pass A1 at a point at the upper end of the warmsection 106 a. The flow of side stream 400 is regulated by a controlvalve 300. The outlet stream 402 from control valve 300 then flows intopass B1 at the lower end of the warm section 106 a. Further, as shown inFIG. 6 , another side stream 404 is taken from warm pass A1 at a pointat the lower end of the warm section 106 a. The flow of side stream 404is regulated by a control valve 302. The outlet stream 406 from controlvalve 302 then flows into pass B1 lower in the warm section 106 a.

FIG. 7 is the schematic illustration, flow diagram of FIG. 2C with thealternative embodiment of the integrated main heat exchanger 106 splitinto the warm section 106 a and the cold section 106 b. The warm section106 a and the cold section 106 b can be composited of one or more brazedaluminum heat exchanger (BAHX) cores. As shown in FIG. 7 , a side stream400 is taken from warm pass A1 at a point at the upper end of the warmsection 106 a. The flow of side stream 400 is regulated by a controlvalve 300. The outlet stream 402 from control valve 300 then flows intopass B1 at the lower end of the warm section 106 a. Further, as shown inFIG. 7 , another side stream 404 is taken from warm pass A1 at a pointat the lower end of the warm section 106 a. The flow of side stream 404is regulated by a control valve 302. The outlet stream 406 from controlvalve 302 then flows into pass B1 lower in the warm section 106 a.

FIG. 8 is the schematic illustration, flow diagram of FIG. 2D with thealternative embodiment of the integrated main heat exchanger 106 splitinto the warm section 106 a and the cold section 106 b. The warm section106 a and the cold section 106 b can be composited of one or more brazedaluminum heat exchanger (BAHX) cores. As shown in FIG. 8 , a side stream400 is taken from warm pass A1 at a point at the upper end of the warmsection 106 a. The flow of side stream 400 is regulated by a controlvalve 300. The outlet stream 402 from control valve 300 then flows intopass B1 at the lower end of the warm section 106 a. Further, as shown inFIG. 8 , another side stream 404 is taken from warm pass A1 at a pointat the lower end of the warm section 106 a. The flow of side stream 404is regulated by a control valve 302. The outlet stream 406 from controlvalve 302 then flows into pass B1 lower in the warm section 106 a.

FIG. 9 is the schematic illustration, flow diagram of FIG. 3 with thealternative embodiment of the integrated main heat exchanger 106 splitinto the warm section 106 a and the cold section 106 b. The warm section106 a and the cold section 106 b can be composited of one or more brazedaluminum heat exchanger (BAHX) cores. As shown in FIG. 9 , a side stream400 is taken from warm pass A1 at a point at the upper end of the warmsection 106 a. The flow of side stream 400 is regulated by a controlvalve 300. The outlet stream 402 from control valve 300 then flows intopass B1 at the lower end of the warm section 106 a. Further, as shown inFIG. 9 , another side stream 404 is taken from warm pass A1 at a pointat the lower end of the warm section 106 a. The flow of side stream 404is regulated by a control valve 302. The outlet stream 406 from controlvalve 302 then flows into pass B1 lower in the warm section 106 a.

FIG. 10 shows the external refrigeration system option of the processingunit 100 in FIG. 1 . It illustrates configuration of the integrated mainheat exchanger 106, an external refrigeration system, the first stagecold gas-liquid separator 116, the second stage cold gas-liquidseparator 118, the liquid product drum 120, and the liquid product pump122. Similarly to the aforementioned embodiments, the integrated mainheat exchanger 106 may be split into warm section 106 a and cold section106 b and further composited of one or more brazed aluminum heatexchanger (BAHX) cores as shown in FIGS. 4-9 . The differences betweenthe embodiment shown in FIG. 10 and the embodiments shown in FIGS. 2-9include the removal of the expander/compressor systems and the additionof the external refrigeration system.

The external refrigeration system may be a closed-loop refrigerationsystem that provides refrigeration to the effluent gas streams enteringthe processing unit 100. In embodiments, the external refrigerationsystem may utilize and circulate a mixed refrigerant (MR) compositioncomprising one or more hydrocarbon components such as, withoutlimitation, methane, ethane, ethylene, propane, propylene, butanes, orany combinations thereof. An example of an MR composition may be amixture of methane, ethylene, and propane. Further, the externalrefrigeration system may comprise at least one mixed refrigerantcompressor to pressurize the MR stream. The at least one mixedrefrigerant compressor may be a single or multi-stage compressor systemcomprising a discharge cooler after each compressor stage and adischarge vapor/liquid separator after each discharge cooler. Inembodiments, the external refrigeration system may comprise mixedrefrigerant compressor 501, discharge cooler 502, and dischargevapor/liquid separator 503. The discharge vapor/liquid separator 503 mayseparate the MR composition, resulting in two product streams: apressurized and cooled vapor refrigerant stream 513 and a pressurizedand cooled liquid refrigerant stream 512.

The pressurized and cooled vapor refrigerant stream 513 from thedischarge vapor/liquid separator 503 may be at a pressure between about2,500 kPa·G and about 4,000 kPa·G. In embodiments, the dischargevapor/liquid separator 503 may be a standard vapor/liquid flashseparation vessel capable of separating the MR composition into a vaporproduct and a liquid product. Stream 513 may enter at the top ofintegrated main heat exchanger 106 and travel down through pass C1 to becooled and totally liquified by the cold passes B1, B2, B3, B5, B6, andC2 to a temperature between about −100° C. and about −120° C. As such,stream 513 may exit the integrated main heat exchanger 106 as cooledliquid stream 514. Stream 514 may be reduced to a pressure between about150 kPa·G and about 450 kPa·G and further cooled to a temperaturebetween about −105° C. and about −130° C. via a pressure control valve504, resulting in a pressure-reduced, temperature-decreased vapor/liquidmixed stream 515. Stream 515 may then enter at the bottom of integratedmain heat exchanger 106 and travel upward through pass C2 to providerefrigeration to the warm passes such as A1, A2, A3, and C1 throughvaporization of the MR composition. As such, stream 515 may exit theintegrated main heat exchanger 106 as warm, vaporized stream 510 with apressure between about 50 kPa·G and about 350 kPa·G. Stream 510 may flowto the mixed refrigerant compressor 501, such that stream 510 comprisingthe MR composition may be compressed to stream 511, and then cooled andcondensed by the discharge cooler 502, resulting in stream 518. Inembodiments, the discharge cooler 502 may be an air cooler or a watercooler. Stream 518 may finally enter discharge vapor/liquid separator503 to provide the pressurized and cooled vapor refrigerant stream 513and the pressurized and cooled liquid refrigerant stream 512. In someembodiments, the warm, vaporized stream 510 may first travel through asuction scrubber before entering the mixed refrigerant compressor 501.

The pressurized and cooled liquid refrigerant stream 512 from dischargevapor/liquid separator 503 may also be at a pressure between about 2,500kPa·G and about 4,000 kPa·G. In embodiments, stream 512 may enter at thetop of integrated main heat exchanger 106, travel down through pass C3,and exit as a subcooled liquid stream 516. Stream 516 may be reduced inpressure and cooled in temperature via a second pressure control valve505, resulting in a pressure-reduced, temperature-decreased liquidstream 517. Stream 517 may then enter the integrated main heat exchanger106 to combine with stream 515 in pass C2.

FIG. 11 shows the external cascade refrigeration system option of theprocessing unit 100 in FIG. 1 . It illustrates configuration of theintegrated main heat exchanger 106, an external cascade refrigerationsystem, the first stage cold gas-liquid separator 116, the second stagecold gas-liquid separator 118, the liquid product drum 120, and theliquid product pump 122. Similarly to the aforementioned embodiments,the integrated main heat exchanger 106 may be split into warm section106 a and cold section 106 b and further composited of one or morebrazed aluminum heat exchanger (BAHX) cores as shown in FIGS. 4-9 . Thedifferences between the embodiment shown in FIG. 11 and the embodimentsshown in FIGS. 2-9 include the removal of the expander/compressorsystems and the addition of the external cascade refrigeration system.

The external cascade refrigeration system may be a composite of multipleclosed-loop external refrigeration cycles that provide refrigeration tothe effluent gas streams entering the processing unit 100. Inembodiments, the external cascade refrigeration system may comprise afirst external refrigeration cycle and a second external refrigerationcycle. The first external refrigeration cycle may utilize and circulatea refrigerant comprising propane, or propylene, or any combinationsthereof. Further, the first external refrigeration cycle may comprise arecycle compressor 601, to pressurize the refrigerant, and athermosiphon vessel 604. The recycle compressor 601 may be a single ormulti-stage compressor system comprising a discharge condenser 602 atits final compression discharge stage. The final stage dischargecondenser 602 may condense the refrigerant resulting in a pressurizedand totally condensed saturated liquid refrigerant stream 613.

The pressurized and totally condensed saturated liquid refrigerantstream 613 from the final stage discharge condenser 602 may be at apressure between about 1,000 kPa·G and about 1,750 kPa·G. Inembodiments, the discharge condenser 602 may be an air cooler or a watercooler. Stream 613 may enter the integrated main heat exchanger 106 andtravel down through pass D1 to be sub-cooled by the cold passes B1, B2,B3, B5, B6, and D2 to a temperature between about −10° C. and about −25°C. As such, stream 613 may exit the integrated main heat exchanger 106as sub-cooled liquid stream 614. Stream 614 may be reduced to a pressurebetween about 15 kPa·G and about 50 kPa·G and further cooled to atemperature between about −30° C. and about −45° C. via a level controlvalve 603, resulting in a pressure-reduced, temperature-decreasedvapor/liquid mixed stream 615. Stream 615 may then enter a thermosiphonvessel 604, which may be a vertical vessel configured to maintain asteady internal liquid level. The steady internal liquid level may allowfor the formation of a thermosiphon that may be capable of circulating acold liquid refrigerant stream 616 from the bottom of the thermosiphonvessel 604, through pass D2 of the integrated main heat exchanger 106,and then back to an upper inlet of the thermosiphon vessel 604 as atwo-phase refrigerant stream 617. Stream 617 may comprise between about30% and about 50% vapor in order to maintain a steady operation of thethermosiphon circulation. In embodiments, the cold liquid refrigerantstream 616 which travels upward through pass D2 may vaporize to providerefrigeration to the warm passes such as A1, A2, D1, and E1. Finally, aflashed vapor stream 610 resulting from the thermosiphon vessel 604 mayflow to the recycle compressor 601, such that stream 610 comprising therefrigerant may be compressed to stream 612, and then cooled andcondensed by the final stage discharge condenser 602, resulting instream 613. In some embodiments, the flashed vapor stream 610 may firsttravel through a suction scrubber before entering the recycle compressor601.

The second external refrigeration cycle may utilize and circulate analternate refrigerant comprising ethane, or ethylene, or anycombinations thereof. Alternatively, the alternate refrigerant maycomprise a mixture of methane and ethylene or ethane. Further, thesecond external refrigeration cycle may also comprise one or more stagesof recycle compressors (e.g., a first recycle compressor 701 and asecond recycle compressor 702) to pressurize the alternate refrigerantand one or more thermosiphon vessels (e.g., a warm thermosiphon vessel705 and a cold thermosiphon vessel 707). The one or more recyclecompressors (701/702) may be a multi-stage compressor system comprisinga discharge cooler 703 at its final compression discharge stage. Thefinal stage discharge cooler 703 may cool the alternate refrigerantresulting in a pressurized and cooled refrigerant stream 714.

The pressurized and cooled refrigerant stream 714 from the final stagedischarge cooler 703 may be at a pressure between about 1650 kPa·G andabout 1,950 kPa·G. In embodiments, the discharge cooler 703 may be anair cooler or a water cooler. Stream 714 may enter the integrated mainheat exchanger 106 and travel down through pass E1 to be cooled andtotally condensed by the cold passes B1, B2, B3, B5, B6, and D2 to atemperature between about −30° C. and about −40° C. As such, stream 714may exit the integrated heat exchanger 106 as a cooled and totallycondensed liquid stream 715. Steam 715 may be reduced to a pressurebetween about 450 kPa·G and about 700 kPa·G and further reduced itstemperature to between about −50° C. and about −70° C. via a levelcontrol valve 704, resulting in a pressure-reduced, temperaturedecreased vapor/liquid mixed stream 716. Stream 716 may enter the warmthermosiphon vessel 705 which, similar to thermosiphon vessel 604, maybe a vertical vessel configured to maintain a steady internal liquidlevel. The steady internal liquid level may allow for the formation of athermosiphon that may be capable of circulating a warm liquidrefrigerant stream 718 from the bottom of the warm thermosiphon vessel705, through pass E2 of the integrated main heat exchanger 106, and thenback to an upper inlet of the warm thermosiphon vessel 705 as atwo-phase refrigerant stream 719. Stream 719 may comprise between about30% and about 50% vapor in order to maintain a steady operation of thethermosiphon circulation. In embodiments, the warm liquid refrigerantstream 718, which travels upward through pass E2, may vaporize toprovide refrigeration to the warm passes such as A1 and A3. A flashedvapor stream 720, resulting from the warm thermosiphon vessel 705, mayflow to and mix with any recycle compressor discharge stream from anycompression discharge stage previous to the final compression dischargestage. In embodiments, the flashed vapor stream 720 may flow to and mixwith a first stage recycle compression discharge stream 711 from thefirst recycled compressor 701 to result in a feed stream 712 that mayflow to the second recycled compressor 702, such that stream 712comprising the alternate refrigerant may be compressed to stream 713,and then cooled by the final stage discharge cooler 703, resulting instream 714. In some embodiments, the feed stream 712 may first travelthrough a suction scrubber before entering the second recycle compressor702.

In further embodiments, an additional warm liquid refrigerant stream 721may be drawn from stream 718 at the bottom of warm thermosiphon vessel705. Stream 721 may be reduced to a pressure between about 5 kPa·G andabout 50 kPa·G and further reduced its temperature to between about −95°C. to about −115° C. via a level control valve 706, resulting in apressure-reduced, temperature-decreased liquid stream 722. Stream 722may enter the cold thermosiphon vessel 707 which, also similar tothermosiphon 604, may be a vertical vessel configured to maintain asteady internal liquid level. The steady internal liquid level may allowfor the formation of a thermosiphon that may be capable of circulating acold liquid refrigerant stream 723 from the bottom of the coldthermosiphon vessel 707, through pass E3 of the integrated main heatexchanger 106, and then back to an upper inlet of thermosiphon 707 as atwo-phase refrigerant stream 724. Stream 724 may comprise between about30% and about 50% vapor in order to maintain a steady operation of thethermosiphon circulation. In embodiments, the cold liquid refrigerantstream 723, which travels upward through pass E3, may vaporize toprovide refrigeration to the warm passes such as A1 and A3. Finally, aflashed vapor stream 710, resulting from the thermosiphon vessel 707,may flow to the first recycle compressor 701, such that stream 710comprising the alternate refrigerant may be compressed, resulting in thefirst stage recycle compression discharge stream 711. In someembodiments, the flashed vapor stream 710 may first travel through asuction scrubber before entering the first recycle compressor 701.

Further differences between the embodiments shown in FIGS. 10-11 , andthe embodiments shown in FIGS. 2-9 include the removal of pass B4 andthe altered path flow of stream 232. As illustrated in FIGS. 10 and 11 ,stream 232 may enter at the bottom of integrated main heat exchanger 106and travel upward through pass B3 such that the stream 232 may be warmedand exit the integrated main heat exchanger 106 as the net gas product212. Further, stream 220, which in previous embodiments was a resultingstream from the expander system, may now be a stream split from stream232. In embodiments, stream 220 may be the result of a stream 264 splitfrom stream 232 that may be reduced to a pressure between about 195kPa·G and about 450 kPa·G and cooled to a temperature between about −95°C. and about −125° C. via a flow control valve 136. As with previousembodiments, stream 220 may enter the integrated main heat exchanger 106where it mixes with outlet stream 218 of flow control valve 124. Themixed stream of stream 220 and outlet stream 218 may travel upwardthrough pass B1, where heat exchanging occurs between the cold streampass B1 and warm stream passes A1, A2, A3, and A4, as well as C1, C3,D1, and E1. Before exiting through pass B1, the mixed stream iscompletely vaporized and becomes a superheated vapor stream. Thesuperheated vapor stream is referred to as combined feed 202 afterexiting pass B1. The pressure of combined feed 202 is maintained at aconstant value by the feed of the dehydrogenation unit 102 (not shown).The combined feed 202 is the reactor feedstock for dehydrogenation unit102 (not shown).

FIG. 12 shows the “no recycle gas” option of the processing unit 100 inFIG. 10 . In FIG. 10 , the fresh feed 200 and the recycle gas stream 220may be mixed and vaporized in the heat exchanger 106 of the processingunit 100, thereby providing the combined feed 202. However, FIG. 12shows an alternative embodiment that processes and/or vaporizes freshfeed 200, without combining the recycle gas stream 220, therebyproviding an alternative combined feed 202. It illustrates configurationof the integrated main heat exchanger 106, the external refrigerationsystem, the first stage cold gas-liquid separator 116, the second stagecold gas-liquid separator 118, the liquid product drum 120, and theliquid product pump 122, as well as a plurality of fresh feed controlvalves 350, a plurality of fresh feed thermosiphon vessels 352, and oneor more vapor fresh feed compressors 354. Similarly to theaforementioned embodiments, the integrated main heat exchanger 106 maybe split into warm section 106 a and cold section 106 b and furthercomposited of one or more brazed aluminum heat exchanger (BAHX) cores asshown in FIGS. 4-9 . The differences between the embodiment shown inFIG. 12 and the embodiment shown in FIG. 10 may include the removal ofthe recycle gas stream 220/264 and their corresponding control valve136. By this removal of the recycle gas stream 220, fresh feed 200 maybe processed and/or vaporized differently within processing unit 100.Therefore, further differences between the embodiments may include theremoval of control valves 124, 300, and 302, their corresponding sidestreams and outlet streams 216, 218, 400, 402, 404, and 406, and passA1, as well as the addition of the plurality of fresh feed controlvalves 350, the plurality of fresh feed thermosiphon vessels 352, andthe one or more vapor fresh feed compressors 354.

As illustrated in FIG. 12 , fresh feed 200 may be divided into aplurality of split streams 410, each at any suitable pressure andtemperature. In embodiments, each of the plurality of split streams 410may be reduced to a pressure between about 50 kPa·G and about 200 kPa·Gand further cooled to a temperature between about −35° C. and about −15°C., or alternatively between about −15° C. and about 5° C., via theplurality of fresh feed control valves 350, resulting in a plurality ofpressure-reduced, temperature-decreased split streams 411. Each of theplurality of streams 411 may enter the plurality of fresh feedthermosiphon vessels 352, respectively. Each of the plurality of freshfeed thermosiphon vessels 352 may be vertical vessels configured tomaintain a steady internal liquid level. The steady internal liquidlevel may allow for the formation of a thermosiphon that may be capableof circulating a cold fresh feed liquid stream 412 from the bottom ofeach of the plurality of fresh feed thermosiphon vessel 352, through apass B7 at about the middle of the warm section 106 a of the main heatexchanger 106, then back into an upper inlet of each of the plurality offresh feed thermosiphon vessels 352 as a two-phase stream 413,comprising a vapor phase and a liquid phase. For instance, each of theplurality of two-phase streams 413 may comprise between about 30% andabout 50% vapor in order to maintain steady operation of thethermosiphon circulation. In embodiments, the liquid phase of each ofthe plurality of two-phase streams 413 may be combined to each of theplurality of cold fresh feed liquid streams 412 which travel upwardthrough respective passes B7 and vaporize to provide cooling to the warmpasses such as A2, C1, and C3. In addition, each of the plurality offresh feed thermosiphon vessels 352 may provide a flashed cold freshfeed vapor stream 414, which may include the vapor phase of each of theplurality of two-phase streams 413. Each of the plurality of flashedcold fresh feed vapor streams 414 may enter the integrated main heatexchanger 106 at about the middle of the warm section 106 a and travelupward through respective passes B8, thus providing additional coolingto the warm passes A2, C1, and C3. Furthermore, as each of the pluralityof flashed cold fresh feed vapor streams 414 travel through theirrespective passes B8, the streams 414 may be warmed to temperaturesclose to that of the reactor effluent 210, thus becoming a plurality ofsuperheated vapor streams 415 upon exit at the upper end of the warmsection 106 a of main heat exchanger 106. In embodiments, one of theplurality of superheated vapor streams 415 may include a final-stagesuperheated vapor stream 422. Each of the plurality superheated vaporstreams 415, excluding the final-stage superheated vapor stream 422, maybe compressed to a pressure between about 200 kPa·G and about 450 kPa·Gvia the one or more fresh feed vapor compressors 354, resulting in oneor more compressed superheated vapor streams 416. Finally, the one ormore compressed superheated vapor streams 416 may be comingled, alongwith the final-stage superheated vapor stream 422, resulting in thealternative combined feed 202. The pressure of the alternative combinedfeed stream 202 may be maintained at a constant value by the feed of thedehydrogenation unit 102 (not shown). The alternative combined feed 202may once again be a reactor feedstock for dehydrogenation unit 102 (notshown). For solely illustrative purposes, FIG. 12 shows two splitstreams 410, two fresh feed control valves 350, two fresh feedthermosiphon vessels 352, two passes B7, two passes B8, one superheatedvapor stream 415, one final-stage superheated vapor stream 422, and onevapor fresh feed compressor 354. However, the processing unit 100 maycomprise any suitable number of split streams 410, fresh feed controlvalves 350, fresh feed thermosiphon vessels 352, passes B7 and B8, andvapor fresh feed compressors 354.

As further illustrated in FIG. 12 , reactor effluent 210, anolefin-hydrogen effluent stream from the reactor effluent compressorunit 104 (not shown), enters pass A2 at the upper warm end of the warmsection 106 a of the integrated main heat exchanger 106, where thestream is cooled to a low temperature as it flows through and exits passA2 at the lower end of the warm section 106 a of the integrated mainheat exchanger 106. The cooling of the reactor effluent 210 as ittravels through pass A2 is caused by cold stream passes B3, B5, B6, B7,B8 and C2. Outlet stream 222 from pass A2 enters the first stage coldgas-liquid separator 116 with a low temperature, at which time amajority, >95%, of the olefin and heavy paraffinic components in outletstream 222 are condensed to liquid, which is separated out as liquidstream 224. Further, almost all, >99% of the hydrogen from outlet stream222 remains vapor, and the first stage cold gas-liquid separator 116separates out the vapor as vapor stream 226.

The vapor stream 226 then flows back to the upper end of the coldsection 106 b of the integrated main heat exchanger 106 through pass A3,where it is cooled to a lower temperature by the time it exits pass A3at the lower end of the cold section 106 b of the integrated main heatexchanger 106. The outlet stream 228 from pass A3 enters the secondstage cold gas-liquid separator 118, where almost all, >85%, of theolefin and heavy paraffinic components in an outlet stream 228 arecondensed to a liquid stream 245 and almost all, >99.95% of the hydrogenstays in a cold vapor stream 232. The cold vapor stream 232 exits secondstage cold gas-liquid separator 118 and returns to the lower end of thecold section 106 b of the integrated main heat exchanger 106 at pass B3.The cold vapor stream 232 travels up pass B3, where it exchanges heatwith warm stream passes A3, A2, C1 and C3. As such cold vapor stream 232may be warmed as it travels through pass B3. Upon exiting pass B3 at theupper end of the warm section 106 a of the integrated main heatexchanger 106, the temperature of cold vapor stream 232 may be atemperature close to the inlet temperature of pass A2. The outlet stream262 from pass B3 is typically regulated by a control valve 130 tomaintain the pressure of the second stage cold gas-liquid separator 118.The outlet stream of control valve 130 is the net gas product 212, whichmay be sent to a downstream production facility.

Returning to the first stage cold gas-liquid separator 116, the pressureof the olefin-rich liquid stream 224 is reduced by level control valve138 before it enters the liquid product drum 120 as cold stream 246.

Returning to the second stage cold gas-liquid separator 118, theolefin-rich liquid stream 245 may be split into two streams 241 and 247,with stream 247 having about 15% to 20% of the total flow of the stream245. The pressure of the olefin-rich liquid stream 241 is reduced bylevel control valve 141, resulting in a pressure-reduced stream 243which may enter pass B2 from the lower end of the cold section 106 b ofthe main heat exchanger 106. In embodiments, the pressure-reduced stream243 may be a cold stream that exchanges heat with the warm passes A3 andC1, becoming a partially vaporized stream 248. This partially vaporizedstream 248 exits pass B2 at the upper end of the cold section 106 b ofthe integrated main heat exchanger 106 and flows to the liquid productdrum 120, combining with the cold stream 246. As for stream 247, flowcontrol valve 119 may reduce the pressure of stream 247, resulting in areduced-pressure stream 230 which may enter the top of rectifier 140 asthe rectifier's reflux liquid.

A combined liquid stream 249 from stream 246 and 248 may enter theliquid product drum 120, where light components, mainly hydrogen,methane, ethane, and maybe some C3+ components, flash out from theliquid and travel upward through the rectifier 140 located on the top ofthe liquid product drum 120 or installed separately from the liquidproduct drum 120. The upward traveling hydrogen-rich gas in therectifier 140, which may be a packed column, makes contact with thedownward traveling colder reflux liquid stream 230 from the second stagecold gas-liquid separator 118. Heat and mass transferring occurs in therectifier 140, and therefore the hydrogen-rich gas in the rectifier 140is further purified to meet the minimum hydrogen content specificationof the flash drum vapor 206, before exiting the top of the rectifier 140as a vapor stream 250.

The pressure of the liquid product drum 120 is maintained by a pressurecontrol valve 142 on vapor stream 250 to a constant pressure to maximizethe recovery of olefin and heavy hydrocarbon components in the liquidproduct 254 and to meet the specification of the maximum allowablehydrogen content in the liquid product 254.

After the pressure control valve 142, a cold stream 252 contains certainolefin components in addition to the main light components hydrogen,methane, and ethane. The cold stream 252 enters cold stream pass B6 atthe lower end of the cold section 106 b of the integrated main heatexchanger 106. As cold stream 252 travels up pass B6, it exchanges heatwith the warm stream passes A3, C1, A2, and C3, and cold stream 252 iswarmed to a temperature close to the inlet temperature of reactoreffluent 210 or fresh feed 200 as it exits pass B6 from the upper end ofthe warm section 106 a of the main heat exchanger 106. The flash drumvapor 206 from pass B6 then flows back to the inlet of the reactoreffluent compressor unit 104 (not shown).

The separated cold liquid stream 254 from the liquid product drum 120 ispumped by the liquid product pump 122 to a pressure that meets therequired pressure of the liquid product 214. The liquid level of theliquid product drum 120 is maintained by a level control valve 144. Thecold liquid product stream 256 then enters pass B5 at the lower end ofwarm section 160 a of the integrated main heat exchanger 106. As theliquid product stream 256 travels upward in pass B5, it exchanges heatwith the warm passes A2, C1 and C3 and is warmed to a temperaturedefined by the liquid product 214 specification as it exits pass B5 atthe upper end of the warm section 106 a of the integrated main heatexchanger 106. The liquid product 214 is then sent to a productionfacility. In embodiments, liquid product drum 120 is elevated to aheight to get enough NPSHa (net positive suction head available) for theliquid product pump 122 to avoid cavitation damage to the liquid productpump 122.

The external refrigeration system illustrated in FIG. 12 may be therefrigeration system as described in FIG. 10 of this disclosure. Inembodiments, the mixed refrigerant compressor 501 of the externalrefrigeration system and the aforementioned one or more vapor fresh feedcompressors 354 may be independently installed within the processingunit 100. Alternatively, the mixed refrigerant compressor 501 and theone or more vapor fresh feed compressors 354 may be integrated into oneintegrally-geared compressor with the processing unit 100.

Further, a coldbox 146 is designed to contain all low-temperatureequipment including the integrated main heat exchanger 106, the firststage cold gas-liquid separator 116, the second stage cold gas-liquidseparator 118, the liquid product drum 120, the plurality of fresh feedthermosiphon vessels 352, as well as the associated piping. Controlvalves 350, 138, 141, 119, 142, and 124 can either be enclosed within orinstalled outside of the coldbox 146. The coldbox 146 is typicallyfilled with insulation material and purged with nitrogen to provide coldinsulation for the low-temperature equipment and parts.

Generally, the above describes an improved process and system forseparation of hydrogen from an effluent by dehydrogenation of propane,isobutane, or a mixture of both. More specifically, the use of anintegrated heat exchanger allows for a more balanced process reducingoff-design, i.e. not allowed for or expected, flow distributions. Thisprovides improved thermodynamic efficiency and stability. Further, anintegrated heat exchanger with a compact design takes up less space,which can be a significant benefit in an industrial setting.

Further, the expander configuration with two sets ofexpanders/compressors improves the process. In the description above,the composition and mass flow of the stream to each set ofexpander/compressor remains substantially unchanged. This improves theenergy benefit by recovering the expander power back to the system.Also, the hydrogen-rich gas in the rectifier is further purified to meetthe minimum hydrogen content specification of the flash drum vapor,which in turn improves the C₃ liquid product recovery.

Referring to FIG. 12 , in embodiments liquid product 214 may mainlycomprise propylene and propane, as well as small amounts of lightercomponents such as hydrogen, methane, ethylene, and ethane. An exampleof the composition of liquid product 214 is shown in the following Table1000-1:

TABLE 1000-1 Components Mole % Notes Hydrogen 0.0556 May be as high as0.1000% Methane 0.1413 Ethylene 0.0835 Ethane 1.7337 Propylene 29.5787May be as high as 35% Propane 67.9940 C4+ Heavy 0.4131 HC Total 100.0000

In embodiments, the light components, such as ethane and all otherlighter components, may need to be removed from liquid product 214,which may be accomplished using a deethanizer system 1000 and apropylene/propane splitter system 800. In embodiments, polymer-gradepropylene typically comprises a minimum purity of 99.5%-99.8% (mole)propylene and may contain impurities such as methane ethylene, ethane,propane, etc.

FIG. 13 illustrates an additional embodiment of the separation system ofprocessing unit 100 shown in FIG. 12 , wherein FIG. 13 comprises thedeethanizer system 1000 and the propylene/propane splitter system 800.

In embodiments, liquid product 214 may flow to the middle stage of astripper column 1601. In embodiments, liquid product 214 may have apressure in a range of between 1,400 kPa·G to 1,600 kPa·G and atemperature in a range of between 30° C. to 45° C. Further, inembodiments, liquid product 214 may comprise mainly propylene andpropane, as well as certain amounts of light components such ashydrogen, methane, ethylene, and ethane. An example of a composition ofliquid product 214 is shown in Table 1000-1. In embodiments, strippercolumn 1601 may comprise a tray-type column or a packing-type column. Inembodiments, a reflux liquid stream 1633 may be fed into the top stageof stripper column 1601, and reboiling vapor streams 1643 and 1645 maybe fed into the bottom stage of stripper column 1601. In embodiments,heat and mass transfers may occur while liquid product 214, refluxliquid stream 1633, and reboiling vapor streams 1643 and 1645 travelinto and contact the trays and/or packing inside stripper column 1601,which may form a bottom C3+ hydrocarbon stream 1641 with less than 100ppm ethane and lighter components. In embodiments, a top vapor stream1630 may still contain amounts of C3+ hydrocarbons, and therefore, thetop vapor stream 1630 may require additional purification and recoveryby a rectifier column 1603. In embodiments, the ethane and lightercomponents in vapor stream 1630 may be significantly enriched withethane and lighter components greater than 55% (mole).

In embodiments, a fresh feed stream 930, which may be split from themain fresh feed stream 200, may flow to a fresh feed/vapor heatexchanger 902, which may reduce the temperature of the fresh feed stream930 to about 10° C. to 15° C. In embodiments, this reduction intemperature of the fresh feed stream 930 in heat exchanger 902 may beassisted by a cold fresh feed vapor stream 933. In embodiments, a liquidstream 931 may emerge from heat exchanger 902 and proceed to a controlvalve 901. In embodiments, the pressure of liquid stream 931 may bereduced by control valve 901, which may result in reducing the pressureof liquid stream 931 to a range of between 250 kP·G to 400 kPa·G(depending on the pressure of the combined feed 202 as required bydehydrogenation unit 102) to become a liquid/vapor mixture stream 932,which may have a temperature ranging from about −10° C. to about 1.5° C.In embodiments, stream 932 may be routed to a stripper column condenser1602, which may cool the vapor stream 1630. In embodiments, saturatedvapor stream 933 may emerge from the stripper column condenser 1602, andsaturated vapor stream 933 may proceed to heat exchanger 902 wheresaturated vapor stream 933 may exchange heat with warm fresh feed stream930. In embodiments, a vapor stream 934 may emerge from heat exchanger902, and vapor stream 934 may proceed to combine with combined feed 202.

In embodiments, a vapor stream 1631 may emerge from stripper columncondenser 1602 with a temperature of about 0° C. to 5° C., and vaporstream 1631 may partially (around 90%) condense to liquid. Inembodiments, stream 1631 may proceed to the bottom of rectifier column1603, wherein any vapor remaining in stream 1631 may be flashed out. Inembodiments, once within the rectifier column 1603, the vapor materialsfrom stream 1631 may travel upwards in the rectifier column 1603providing stripping to the materials from a liquid stream 1637 fed fromthe top of the rectifier column 1603, and further, the liquid fromstream 1631 may be separated out and combined with the materials fromliquid stream 1637 to form a cold reflux stream 1632. In embodiments,cold reflux stream 1632 may proceed to a stripper column reflux pump1604, wherein cold reflux stream 1632 emerges as stream 1633. Inembodiments, stream 1633 may proceed back to the top stage of strippercolumn 1601.

Returning to stream 1641, in embodiments the C3+ hydrocarbon stream 1641emerging from the bottom of the stripper column 1601 may be split intothree streams: a stream 1642, which may flow to a stripper column mainreboiler 1609; a stream 1644, which may flow to a stripper columnsupplemental reboiler 1610; and a C3+ liquid product stream 1646, whichmay flow to a pressure control valve 1611, where it may become a stream1647, which then proceeds to the propylene/propane splitter system 800(detail not shown) to separate the propylene product.

In embodiments, stream 1641 may have a temperature range of between 25°C. to 35° C. depending on the operation pressure of stripper column1601, which is typically in a range of between 850 kPa·G to 1150 kPa·G.In embodiments, stream 1642 may be heated by a warm gas stream 810 splitfrom a heat pump compressor (HPC) discharge at the propylene/propanesplitter system 800 (detail not shown). In embodiments, the typicaltemperature of stream 810 may range from between 45° C. to 55° C. Inembodiments, stream 810 may be cooled by stream 1642 through thestripper column main reboiler 1609 to a temperature range of 28° C. to32° C., and a stream 811 may flow to the propylene/propane splittersystem 800. In embodiments, stream 1642 may be vaporized in strippercolumn main reboiler 1609 becoming stream 1643, which may be routed backto the bottom stage of stripper column 1601 to provide stripping to thedown-coming liquid from stream 214 and stream 1633. In embodiments,stripper column main reboiler 1609 may be designed to provide 90%-95% ofthe required reboiling duty of stripper column 1601, while the remaining5% to 10% of the required reboiling duty may be provided by strippercolumn supplemental reboiler 1610. In embodiments, this design mayprovide operation flexibility and stability for the reboiling section ofstripper column 1601. In embodiments, the heating medium for strippercolumn supplemental reboiler 1610 may comprise a temperature greaterthan 40° C. material, such as the plant cooling water return stream.Alternatively, in other embodiments the heating medium may compriseliquid refrigerant stream 512.

In embodiments, stripper column 1601 may be operated at a pressureranging from between about 850 kPa·G to about 1150 kPa·G, with atemperature of the top of stripper column 1601 ranging from between−5.0° C. to 5° C. and a temperature of the bottom of stripper column1601 ranging from between 25° C. to 35° C. In embodiments, this mayproduce less than about 100 ppm ethane and lighter components in the C3+product stream 1647.

In embodiments, rectifier column 1603 may operate at about the samepressure as stripper column 1601. In embodiments, rectifier column 1603may be a tray-type column or a packing-type column, wherein a refluxliquid stream 1637 may flow into the top stage of rectifier column 1603and further wherein stripping vapor stream 1631 may flow into the bottomstage of rectifier column 1603. In embodiments, heat and masstransferring may occur when the liquid and vapor in rectifier column1603 travel through and contact the trays or packing inside rectifiercolumn 1603, which may form bottom stream 1632, and overhead vaporstream 1634 composed primarily of ethane and lighter components. Inembodiments, overhead vapor stream 1634 may proceed to a rectifiercolumn reflux condenser 1605, where stream 1634 may be cooled to about−36° C. to −32° C. and emerge as a stream 1635. In embodiments, thecooling for stream 1634 may be a result of a refrigerant stream 1735entering rectifier column reflux condenser 1605. In embodiments, stream1635 may be partially condensed by rectifier column reflux condenser1605, and stream 1635 may flow to a rectifier column reflux drum 1606,where the vapor and liquid in stream 1635 may be separated. Inembodiments, a liquid stream 1636 may emerge from the bottom ofrectifier column reflux drum 1606 and may proceed to a rectifier columnreflux pump 1608, after which stream 1636 emerges as stream 1637, whichmay be pumped back to the top stage of rectifier column 1603. Inembodiments, a cold vapor stream 1638 emerging from rectifier columnreflux drum 1606 may be C3+ hydrocarbon free and therefore comprisemainly ethane and lighter components. In embodiments, stream 1638 mayflow to the refrigerant/gas heat exchanger 1703, where stream 1638 mayexchanges heat with a warm refrigerant liquid stream 1732 and may bewarmed to a temperature within the range of about 30° C. to 35° C.,emerging from heat exchanger 1703 as a stream 1639. In embodiments, thepressure of stream 1639 may be regulated by a pressure control valve1607 to maintain the system pressure of stripper column 1601 andrectifier column 1603. In embodiments, a discharge stream 1640 frompressure control valve 1607 may be routed to a fuel gas system (notshown).

In embodiments, rectifier column 1603 may be operated at a pressureranging from about 850 kPa·G to about 1150 kPa·G with a temperatureranging from −36° C. to −32° C. at top of the rectifier column 1603 anda temperature ranging from −5° C. to 5° C. at the bottom of therectifier column 1603. In embodiments, this may result in about 100% C3+recovery to C3+ product stream 1647.

In embodiments, the cooling of rectifier column condenser 1605 may bedue to a vapor-compression refrigeration system. In embodiments, arefrigeration compressor 1701 may boost a saturated refrigerant vaporstream 1730 from rectifier column reflux condenser 1605 to a highpressure. In embodiments, refrigerant vapor stream 1731 may be condensedto a saturated refrigerant liquid stream 1732 by a refrigerant condenser1702. In embodiments, refrigerant condenser 1702 may be water cooler orair cooler. In embodiments, stream 1732 may have a temperature rangingfrom about 30° C. to 50° C. In embodiments, saturated refrigerant liquidstream 1732 may be further cooled by cold vapor stream 1638 inrefrigerant/gas heat exchanger 1703 to a subcooled condition and thenrouted to a refrigerant receiver vessel 1704 as stream 1733. Inembodiments, the pressure of a subcooled refrigerant liquid stream 1734from refrigerant receiver vessel 1704 may be reduced through athermal-expansion valve 1705, resulting in stream 1735, which may have acold temperature of about −45° C. to −35° C. through an adiabatic flashevaporation of part of the liquid refrigerant. In embodiments, coldrefrigerant stream 1735 may be routed to the rectifier column refluxcondenser 1605 to provide refrigeration to rectifier column overheadstream 1634 by vaporizing the cold refrigerant liquid in stream 1735. Inembodiments, stream 1735 may totally vaporize in rectifier column refluxcondenser 1605, which may result in saturated refrigerant vapor stream1730, which may be routed to refrigerant compressor 701 for compression.

In embodiments, a suitable refrigerant for the refrigeration system maybe propane or propylene. In embodiments, the propane may be charged fromfresh feed (propane) stream 200, while the propylene may be charged frompropylene product stream from the propylene/propane splitter system 800(not shown in detail). In embodiments, the refrigeration system may beoptimized by adding an economizer (not shown) to lower the compressorenergy consumption. Further, in embodiments, the refrigerationcompressor 1701 may be a centrifugal type compressor or a screw typecompressor.

Referring to FIG. 14 , in embodiments the vapor-compressionrefrigeration system for the rectifier column condenser 1605 mayalternate to a refrigeration process by flashing a part of fresh feed(propane) stream 200. In embodiments, a fresh feed stream 1741, whichmay be split from the main fresh feed stream 200, may flow to a freshfeed/gas heat exchanger 1711, which may reduce the temperature of thefresh feed stream 1741 to about −35° C. to −25° C. In embodiments, thisreduction in temperature of the fresh feed stream 1741 in heat exchanger1711 may be assisted by a cold fresh feed vapor stream 1744 and the coldvapor stream 1638. In embodiments, a liquid stream 1742 may emerge fromheat exchanger 1711 and proceed to a control valve 1712. In embodiments,the pressure of liquid stream 1742 may be reduced by control valve 1712,which may result in reducing the pressure of liquid stream 1742 to arange of between 10 kP·G to 50 kPa·G (depending on the requiredtemperature of stream 1635) to become a liquid/vapor mixture stream1743, which may have a temperature ranging about −40° C. to about −35°C. In embodiments, stream 1743 may be routed to the rectifier columncondenser 1605, which may cool the vapor stream 1634. In embodiments,saturated vapor stream 1744 may emerge from the rectifier columncondenser 1605, and saturated vapor stream 1744 may proceed to heatexchanger 1711 where saturated vapor stream 1744 may exchange heat withwarm fresh feed stream 1741. In embodiments, a vapor stream 1745 with atemperature ranging from 30° C. to about 45° C. may emerge from heatexchanger 1711, and vapor stream 1745 may be boosted to a pressure sameas stream 934 by a fresh feed vapor booster compressor 1713. Inembodiments, a vapor stream 1746 may emerge from the discharge of thefresh feed vapor booster compressor 1713 and proceed to combine withstream 934 and then commingle with the combined feed 202. Inembodiments, the fresh feed vapor booster compressor 1713 may comprise acentrifugal type compressor, a screw type compressor, or a reciprocatingtype compressor.

In embodiments, similar to FIG. 13 , cold vapor stream 1638 emergingfrom rectifier column reflux drum 1606 may be C3+ hydrocarbon free andtherefore comprise mainly ethane and lighter components. In embodiments,stream 1638 may flow to the fresh feed/gas heat exchanger 1711, wherestream 1638 may exchanges heat with warm fresh feed liquid stream 1741and may be warmed to a temperature within the range of about 30° C. to45° C., emerging from heat exchanger 1711 as a stream 1639. Inembodiments, the pressure of stream 1639 may be regulated by a pressurecontrol valve 1607 to maintain the system pressure of stripper column1601 and rectifier column 1603. In embodiments, a discharge stream 1640from pressure control valve 1607 may be routed to a fuel gas system (notshown).

In embodiments, the fresh feed/vapor heat exchanger 902 and therefrigerant/gas heat exchanger 1703 may be shell/tube type heatexchangers or brazed aluminum plate-fin type heat exchangers (BAHX), andthe latter may significantly increase the system thermal efficiencysince it can be designed to have an approaching temperature as low as1.0° C. In embodiments, the fresh feed/gas heat exchanger 1711 may bebrazed aluminum plate-fin type heat exchangers (BAHX), and maysignificantly increase the system thermal efficiency since it can bedesigned to have an approaching temperature as low as 1.0° C. Inembodiments, the stripper column reflux condenser 1602, the strippercolumn main reboiler 1609, the stripper column supplemental reboiler1610, and rectifier column reflux condenser 1605 may be shell/tube typeheat exchangers, or brazed aluminum plate-fin in kettle (PFK) type heatexchangers, and the latter may significantly increase the system thermalefficiency since it can be designed to have an approaching temperatureas low as 1.0° C. to 2.0° C.

In embodiments, the disclosed processes and schemes of the deethanizersystem 1000 may operate at lower pressures and temperatures at thecolumns 1601 and 1603, which may reduce the overall system energyconsumption, equipment sizes, and equipment cost compared to thetraditional deethanizer system that typically operates at a higherpressure ranging about from 2500 kPa·G to 3000 kPa·G.

In embodiments, the disclosed processes and schemes of the deethanizersystem 1000 may operate at a lower pressure and a lower temperature atthe bottom of the stripper column 1601, which may enable using lowertemperature heating sources for reboilers 1609 and 1610, thereforeeliminating low-pressure steam as heating medium, which the traditiondeethanizer systems typically uses. In embodiments, lower temperatureheating sources such as the HPC discharge stream, the MR liquid stream512, and/or a plant cooling water return stream may be used as heatingmediums for the reboilers 1609 and 1610.

In embodiments, the elimination of low-pressure steam as a heatingsource in the disclosed process and schemes of the deethanizer system1000 may reduce the steam consumption by 0.55 metric tons per metric tonof propylene production. This is therefore a significant reduction ofplant CO2 emissions given the steam is typically produced by burningfossil fuels.

FIG. 15 illustrates an alternative embodiment in which the refrigerationprocess by flashing a part of the fresh feed (propane) stream 200 tocool the rectifier column reflux condenser 1605 may be replaced byrefrigeration obtained from the cold section 106 b of the integratedmain heat exchanger 106.

Referring to FIG. 15 , in embodiments the overhead vapor stream 1634 mayproceed to a pass D1 in the cold section 106 b of the integrated mainheat exchanger 106, where overhead vapor stream 1634 may be cooled to atemperature of about −100° C. to about −32° C. and may emerge as stream1635. In embodiments, stream 1635 may be partially condensed. Further,in embodiments, stream 1635 may flow to rectifier column reflux drum1606, wherein the vapor and liquid in stream 1635 may be separated. Inembodiments, liquid stream 1636 may emerge from the bottom of therectifier column reflux drum 1606 and may proceed to rectifier columnreflux pump 1608. In embodiments, stream 1637 may emerge from therectifier column reflux pump 1608, and stream 1637 may be pumped to thetop stage of the rectifier column 1603. In embodiments, cold vaporstream 1638 may emerge from rectifier column reflux drum 1606. Inembodiments, cold vapor stream 1638 may be C3+ hydrocarbon free and maysubstantially comprise ethane and lighter components. In embodiments,stream 1638 may be regulated by pressure control valve 1607 to maintainthe system pressure of stripper column 1601 and rectifier column 1603.In embodiments, discharge stream 1640 may emerge from pressure controlvalve 1607, and discharge stream 1640 may be routed to a fuel gas systemafter exchanging heat with other warm streams (not shown).

What is claimed:
 1. A deethanizer system for separating ethane and othercomponents from a liquid mixture comprising propylene and propanehydrocarbon components as well as ethane and lighter components,comprising: a stripper column section comprising: a stripper column,wherein the stripper column comprises a top stage and a bottom stage,and further wherein the stripper column receives a liquid mixture; and astripper column condenser, wherein the stripper column condenser isconnected to the stripper column and a first heat exchanger, wherein thefirst heat exchanger transfers a fresh feed (propane) liquid stream to afirst control valve, wherein the first control valve transfers a firstmixed vapor/liquid stream to the stripper column condenser; and arectifier column section comprising: a rectifier column, wherein therectifier column is connected to the stripper column condenser, andfurther wherein the rectifier column transfers an overhead vapor streamto an integrated main heat exchanger; a rectifier column reflux drum,wherein the rectifier column reflux drum is connected to the integratedmain heat exchanger, and further wherein rectifier column reflux drumreceives a second mixed vapor/liquid stream from the integrated mainheat exchanger; a rectifier column reflux pump, wherein the rectifiercolumn reflux pump is connected to the rectifier column reflux drum andrectifier column; and a pressure control valve, wherein the pressurecontrol valve is connected to the rectifier column reflux drum; wherein,the deethanizer system is connected to a propylene/propane splittersystem.
 2. The deethanizer system of claim 1, wherein the rectifiercolumn reflux drum transfers a rectifier liquid stream back to therectifier column.
 3. The deethanizer system of claim 2, wherein therectifier column reflux drum transfers the rectifier liquid stream backto the rectifier column through the rectifier column reflux pump.
 4. Thedeethanizer system of claim 1, wherein the first heat exchangerdischarges a discharge vapor stream, and further wherein the first heatexchanger receives a side fresh feed stream and a fresh feed vaporstream.
 5. The deethanizer system of claim 4, wherein the first heatexchanger reduces the temperature of the side fresh feed stream.
 6. Thedeethanizer system of claim 5, wherein the stripper column condenser iscooled by the side fresh feed stream, wherein the side fresh feed streamcomprises a temperature of between −10 degrees C. and 5 degrees C. 7.The deethanizer system of claim 1, wherein the bottom stage of thestripper column discharges a hydrocarbon stream, wherein the hydrocarbonstream is split into a first stream, a second stream, and a thirdstream.
 8. The deethanizer system of claim 7, wherein the first streamflows to a stripper column main reboiler, wherein the stripper columnmain reboiler vaporizes the first stream, and further wherein thestripper column main reboiler sends the vaporized first stream to thebottom stage of the stripper column.
 9. The deethanizer system of claim8, wherein the stripper column main reboiler provides a reboiler streamto the propylene/propane splitter system, and further wherein thepropylene/propane splitter system provides a warmed gas stream to thestripper column main reboiler, and further wherein the warmed gas streamcomprises a temperature between 45 degrees C. and 50 degrees C.
 10. Thedeethanizer system of claim 7, wherein the second stream flows to astripper column supplemental reboiler, wherein the stripper columnsupplemental reboiler vaporizes the second stream by employing a lowertemperature heating source stream with a temperature of between 35degrees C. and 50 degrees C., and further wherein the stripper columnsupplemental reboiler sends the vaporized second stream to the bottomstage of the stripper column.
 11. The deethanizer system of claim 7,wherein the third stream flows to a pressure control valve.
 12. Thedeethanizer system of claim 11, wherein the third stream flows from thepressure control valve to the propylene/propane splitter system.
 13. Thedeethanizer system of claim 1, wherein the system operates at a pressurerange between 850 kPa·G and 1150 kPa·G.
 14. The deethanizer system ofclaim 1, wherein the rectifier column discharges a reflux stream. 15.The deethanizer system of claim 3, wherein the rectifier column refluxdrum transfers the rectifier liquid stream to the rectifier columnreflux pump.
 16. The deethanizer system of claim 15, wherein therectifier column reflux pump transfers the rectifier liquid stream tothe rectifier column.
 17. The deethanizer system of claim 1, wherein therectifier column reflux drum transfers a rectifier vapor stream to thepressure control valve.
 18. The deethanizer system of claim 1, whereinthe integrated main heat exchanger comprises a pass in the cold sectionof the integrated main heat exchanger, and further wherein the passreceives the overhead vapor stream from the rectifier column, andfurther wherein the pass transfers the second mixed vapor/liquid streamto the rectifier column reflux drum.